[Icons] Updates social media icons (#9856)

Updates social media icons by removing them from their containers so
they are more identifiable. Also adds an icon for Twitch.

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### WHY are these changes introduced?

We received feedback that the current icons were hard to distinguish
when next to each other.

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### WHAT is this pull request doing?

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### How to 🎩

🖥 [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)

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  Give as much information as needed to experiment with the component
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<details>
<summary>Copy-paste this code in
<code>playground/Playground.tsx</code>:</summary>

```jsx
import React from 'react';
import {Page} from '../src';

export function Playground() {
  return (
    <Page title="Playground">
      {/* Add the code you want to test in here */}
    </Page>
  );
}
```

</details>

### 🎩 checklist

- [ ] Tested on
[mobile](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md#cross-browser-testing)
- [ ] 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: heyjoethomas

.changeset/chilled-numbers-shop.md

@@ -0,0 +1,5 @@
+---
+'@shopify/polaris-icons': minor
+---
+
+Updates social media icons, removing them from their containers and adds a one for the Twitch platform.

polaris-icons/icons/FacebookMinor.svg

@@ -1,13 +1,12 @@
 name: Facebook
 set: Minor
-description:
-  Facebook logo
+description: Facebook logo
 keywords:
   - facebook
   - social media
 authors:
   - Joe Thomas
 version: 1
 date_added: 2023-07-20
-date_modified: 2023-07-20
+date_modified: 2023-07-28
 exclusive_use:

polaris-icons/icons/FacebookMinor.yml

@@ -1,13 +1,12 @@
 name: Instagram
 set: Minor
-description:
-  Instagram logo
+description: Instagram logo
 keywords:
   - instagram
   - social media
 authors:
   - Joe Thomas
 version: 1
 date_added: 2023-07-20
-date_modified: 2023-07-20
+date_modified: 2023-07-28
 exclusive_use:

polaris-icons/icons/InstagramMinor.svg

@@ -8,5 +8,5 @@ authors:
   - Joe Thomas
 version: 1
 date_added: 2023-07-20
-date_modified: 2023-07-20
+date_modified: 2023-07-28
 exclusive_use:

polaris-icons/icons/InstagramMinor.yml

@@ -9,5 +9,5 @@ authors:
   - Joe Thomas
 version: 1
 date_added: 2023-07-20
-date_modified: 2023-07-20
+date_modified: 2023-07-28
 exclusive_use: