[LegacyTabs] Consolidate se23 styles and logic (#10231)

### WHY are these changes introduced?

Resolves #9946.

### WHAT is this pull request doing?

Consolidates se23 beta styles and logic for `LegacyTabs`.

### How to 🎩

[Storybook](https://5d559397bae39100201eedc1-yxlghuvhen.chromatic.com/?path=/story/all-components-legacytabs--all)
[Prod
Storybook](https://storybook.polaris.shopify.com/?path=/story/all-components-legacytabs--all&globals=polarisSummerEditions2023:true)

🖥 [Local development
instructions](https://github.com/Shopify/polaris/blob/main/README.md#local-development)
🗒 [General tophatting
guidelines](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md)
📄 [Changelog
guidelines](https://github.com/Shopify/polaris/blob/main/.github/CONTRIBUTING.md#changelog)

### 🎩 checklist

- [x] Tested on
[mobile](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md#cross-browser-testing)
- [x] Tested on [multiple
browsers](https://help.shopify.com/en/manual/shopify-admin/supported-browsers)
- [ ] Tested for
[accessibility](https://github.com/Shopify/polaris/blob/main/documentation/Accessibility%20testing.md)
- [ ] Updated the component's `README.md` with documentation changes
- [ ] [Tophatted
documentation](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting%20documentation.md)
changes in the style guide

Author: laurkim

polaris-react/src/components/LegacyTabs/LegacyTabs.scss

@@ -21,7 +21,7 @@ $item-vertical-padding: $item-min-height * 0.5;
 
   .Title {
     width: 100%;
-    padding: var(--p-space-2) var(--p-space-4);
+    padding: var(--p-space-1_5-experimental) var(--p-space-3);
   }
 }
 
@@ -58,24 +58,21 @@ $item-vertical-padding: $item-min-height * 0.5;
     text-decoration: none;
 
     .Title {
-      font-weight: var(--p-font-weight-regular);
-      color: var(--p-color-text);
+      font-weight: var(--p-font-weight-semibold);
+      color: var(--p-color-text-primary);
       background-color: transparent;
+
       // stylelint-disable-next-line selector-max-specificity -- generated by polaris-migrator DO NOT COPY
       &::before {
         background-color: var(--p-color-bg-strong-hover);
       }
-
-      #{$se23} & {
-        color: var(--p-color-text-primary);
-        font-weight: var(--p-font-weight-semibold);
-      }
     }
   }
 
   &:active {
     .Title {
       background-color: transparent;
+
       // stylelint-disable-next-line selector-max-specificity -- generated by polaris-migrator DO NOT COPY
       &::before {
         background: var(--p-color-bg-strong-active);
@@ -85,13 +82,8 @@ $item-vertical-padding: $item-min-height * 0.5;
 
   &:focus-visible {
     .Title {
-      font-weight: var(--p-font-weight-regular);
-      color: var(--p-color-text);
-
-      #{$se23} & {
-        color: var(--p-color-text-primary);
-        font-weight: var(--p-font-weight-semibold);
-      }
+      font-weight: var(--p-font-weight-semibold);
+      color: var(--p-color-text-primary);
     }
 
     &:not(:active) {
@@ -109,8 +101,8 @@ $item-vertical-padding: $item-min-height * 0.5;
 }
 
 .Tab-selected {
-  font-weight: var(--p-font-weight-regular);
-  color: var(--p-color-text);
+  font-weight: var(--p-font-weight-semibold);
+  color: var(--p-color-text-primary);
 
   &:focus .Title {
     outline: var(--p-border-width-3) solid transparent;
@@ -122,20 +114,11 @@ $item-vertical-padding: $item-min-height * 0.5;
 
   .Title {
     outline: var(--p-border-width-3) solid transparent;
-    color: var(--p-color-text);
+    color: var(--p-color-text-primary);
 
     &::before {
       background: var(--p-color-bg-primary);
     }
-
-    #{$se23} & {
-      color: var(--p-color-text-primary);
-    }
-  }
-
-  #{$se23} & {
-    color: var(--p-color-text-primary);
-    font-weight: var(--p-font-weight-semibold);
   }
 }
 
@@ -144,9 +127,10 @@ $item-vertical-padding: $item-min-height * 0.5;
   @include focus-ring;
   border-radius: var(--p-border-radius-1);
   display: block;
-  padding: var(--p-space-2) var(--p-space-4);
+  padding: var(--p-space-1_5-experimental) var(--p-space-3);
   min-width: $item-min-width;
-  color: var(--p-color-text-subdued);
+  color: var(--p-color-text-primary);
+  font-weight: var(--p-font-weight-semibold);
 
   &::before {
     content: '';
@@ -158,12 +142,6 @@ $item-vertical-padding: $item-min-height * 0.5;
     border-top-left-radius: var(--p-border-radius-1);
     border-top-right-radius: var(--p-border-radius-1);
   }
-
-  #{$se23} & {
-    color: var(--p-color-text-primary);
-    font-weight: var(--p-font-weight-semibold);
-    padding: var(--p-space-1_5-experimental) var(--p-space-3);
-  }
 }
 
 .titleWithIcon {

polaris-react/src/components/LegacyTabs/LegacyTabs.tsx

@@ -1,16 +1,11 @@
 import React, {PureComponent} from 'react';
-import {
-  HorizontalDotsMinor,
-  CaretDownMinor,
-  ChevronDownMinor,
-} from '@shopify/polaris-icons';
+import {HorizontalDotsMinor, ChevronDownMinor} from '@shopify/polaris-icons';
 
 import {Box} from '../Box';
 import {Icon} from '../Icon';
 import {Popover} from '../Popover';
 import {classNames} from '../../utilities/css';
 import {useI18n} from '../../utilities/i18n';
-import {UseFeatures} from '../../utilities/features';
 
 import type {TabDescriptor} from './types';
 import {getVisibleAndHiddenTabIndices} from './utilities';
@@ -135,16 +130,7 @@ class TabsInner extends PureComponent<CombinedProps, State> {
     const disclosureButtonContent = hasCustomDisclosure ? (
       <>
         {disclosureText}
-        <UseFeatures>
-          {({polarisSummerEditions2023}) => (
-            <Icon
-              source={
-                polarisSummerEditions2023 ? ChevronDownMinor : CaretDownMinor
-              }
-              tone="subdued"
-            />
-          )}
-        </UseFeatures>
+        <Icon source={ChevronDownMinor} tone="subdued" />
       </>
     ) : (
       <Icon source={HorizontalDotsMinor} tone="subdued" />