Ensure danger buttons have red hover state (#2742)

074cb1a converted links that submit forms to buttons. To keep these
now-buttons looking like links it uses the `link` class. CSS looks for
buttons that are `not(.link)` to continue to style them appropriately.

However any `.button--danger` buttons did not get all the style
overrides. In particular, `:hover` and `:disabled:hover` states fell
back to the normal button background colors (blue).

This fixes those buttons to have the appropriate red hover states.

In addition, `.link--danger` elements also had a blue hover state. I'm
not sure when this was broken, or if it was always supposed to be like
that. Either way, I changed it so they now also appear slightly darker
when hovered to match the buttons.

app/assets/stylesheets/administrate/base/_typography.scss

@@ -32,11 +32,6 @@ a,
   text-decoration-skip-ink: auto;
   transition: color $base-duration $base-timing;
 
-  /* stylelint-disable selector-no-qualifying-type */
-  &.link--danger {
-    color: $red;
-  }
-
   &:hover {
     color: mix($black, $action-color, 25%);
   }
@@ -45,6 +40,14 @@ a,
     outline: $focus-outline;
     outline-offset: $focus-outline-offset;
   }
+  /* stylelint-disable selector-no-qualifying-type */
+  &.link--danger {
+    color: $red;
+  }
+
+  &.link--danger:hover {
+    color: mix($black, $red, 20%);
+  }
 }
 
 hr {

app/assets/stylesheets/administrate/components/_buttons.scss

@@ -52,10 +52,14 @@ button,
 .button--danger {
   background-color: $red;
 
-  &:hover {
+  &:not(.link):hover {
     background-color: mix($black, $red, 20%);
     color: $white;
   }
+
+  &:not(.link):disabled:hover {
+    background-color: mix($black, $red, 20%);
+  }
 }
 
 .button--nav {