Drop all hover mixins

Previously deprecated in v4.x, this clears out the now unused Sass option and removes some unused mixins. Arguably we could remove more, but I like the hover-focus mixin and we make extensive use of it across the project.

scss/mixins/_buttons.scss

@@ -9,7 +9,7 @@
   border-color: $border;
   @include box-shadow($btn-box-shadow);
 
-  @include hover {
+  &:hover {
     color: color-yiq($hover-background);
     @include gradient-bg($hover-background);
     border-color: $hover-border;
@@ -65,7 +65,7 @@
   color: $color;
   border-color: $color;
 
-  @include hover {
+  &:hover {
     color: $color-hover;
     background-color: $active-background;
     border-color: $active-border;

scss/mixins/_hover.scss

@@ -1,37 +0,0 @@
-// Hover mixin and `$enable-hover-media-query` are deprecated.
-//
-// Originally added during our alphas and maintained during betas, this mixin was
-// designed to prevent `:hover` stickiness on iOS-an issue where hover styles
-// would persist after initial touch.
-//
-// For backward compatibility, we've kept these mixins and updated them to
-// always return their regular pseudo-classes instead of a shimmed media query.
-//
-// Issue: https://github.com/twbs/bootstrap/issues/25195
-
-@mixin hover {
-  &:hover { @content; }
-}
-
-@mixin hover-focus {
-  &:hover,
-  &:focus {
-    @content;
-  }
-}
-
-@mixin plain-hover-focus {
-  &,
-  &:hover,
-  &:focus {
-    @content;
-  }
-}
-
-@mixin hover-focus-active {
-  &:hover,
-  &:focus,
-  &:active {
-    @content;
-  }
-}

scss/mixins/_list-group.scss

@@ -6,7 +6,8 @@
     background-color: $background;
 
     &.list-group-item-action {
-      @include hover-focus {
+      &:hover,
+      &:focus {
         color: $color;
         background-color: darken($background, 5%);
       }

scss/mixins/_table-row.scss

@@ -26,7 +26,7 @@
     $hover-background: darken($background, 5%);
 
     .table-#{$state} {
-      @include hover {
+      &:hover {
         background-color: $hover-background;
 
         > td,

scss/mixins/_text-emphasis.scss

@@ -8,7 +8,8 @@
   }
   @if $emphasized-link-hover-darken-percentage != 0 {
     a#{$parent} {
-      @include hover-focus {
+      &:hover,
+      &:focus {
         color: darken($color, $emphasized-link-hover-darken-percentage) !important;
       }
     }