Drop Legacy Edge support.

This allows us to move forward without being held back. Microsoft already replaces the Legacy Edge with the new one on supported Windows versions.

scss/forms/_floating-labels.scss

@@ -61,25 +61,3 @@
   }
   // stylelint-enable no-duplicate-selectors
 }
-
-
-//
-// Fallback for classic Edge
-//
-
-@supports (-ms-ime-align: auto) {
-  .form-floating {
-    display: flex;
-    flex-direction: column-reverse;
-  }
-  .form-floating > label {
-    position: static;
-    padding: 0;
-    margin-bottom: calc(#{$form-floating-padding-y} / 2); // stylelint-disable-line function-disallowed-list
-    border: 0;
-    @include transition(none);
-  }
-  .form-floating > .form-control::-ms-input-placeholder {
-    color: $input-placeholder-color;
-  }
-}

scss/forms/_form-range.scss

@@ -18,7 +18,6 @@
     // No box-shadow() mixin for focus accessibility.
     &::-webkit-slider-thumb { box-shadow: $form-range-thumb-focus-box-shadow; }
     &::-moz-range-thumb     { box-shadow: $form-range-thumb-focus-box-shadow; }
-    &::-ms-thumb            { box-shadow: $form-range-thumb-focus-box-shadow; }
   }
 
   &::-moz-focus-outer {
@@ -78,46 +77,6 @@
     @include box-shadow($form-range-track-box-shadow);
   }
 
-  &::-ms-thumb {
-    width: $form-range-thumb-width;
-    height: $form-range-thumb-height;
-    margin-top: 0; // Edge specific
-    margin-right: $form-range-thumb-focus-box-shadow-width; // Workaround that overflowed box-shadow is hidden.
-    margin-left: $form-range-thumb-focus-box-shadow-width;  // Workaround that overflowed box-shadow is hidden.
-    @include gradient-bg($form-range-thumb-bg);
-    border: $form-range-thumb-border;
-    @include border-radius($form-range-thumb-border-radius);
-    @include box-shadow($form-range-thumb-box-shadow);
-    @include transition($form-range-thumb-transition);
-    appearance: none;
-
-    &:active {
-      @include gradient-bg($form-range-thumb-active-bg);
-    }
-  }
-
-  &::-ms-track {
-    width: $form-range-track-width;
-    height: $form-range-track-height;
-    color: transparent;
-    cursor: $form-range-track-cursor;
-    background-color: transparent;
-    border-color: transparent;
-    border-width: $form-range-thumb-height / 2;
-    @include box-shadow($form-range-track-box-shadow);
-  }
-
-  &::-ms-fill-lower {
-    background-color: $form-range-track-bg;
-    @include border-radius($form-range-track-border-radius);
-  }
-
-  &::-ms-fill-upper {
-    margin-right: 15px; // arbitrary?
-    background-color: $form-range-track-bg;
-    @include border-radius($form-range-track-border-radius);
-  }
-
   &:disabled {
     pointer-events: none;
 
@@ -128,9 +87,5 @@
     &::-moz-range-thumb {
       background-color: $form-range-thumb-disabled-bg;
     }
-
-    &::-ms-thumb {
-      background-color: $form-range-thumb-disabled-bg;
-    }
   }
 }

scss/forms/_form-select.scss

@@ -32,16 +32,6 @@
       // Avoid using mixin so we can pass custom focus shadow properly
       box-shadow: $form-select-focus-box-shadow;
     }
-
-    &::-ms-value {
-      // For visual consistency with other platforms/browsers,
-      // suppress the default white text on blue background highlight given to
-      // the selected option text when the (still closed) <select> receives focus
-      // in Edge.
-      // See https://github.com/twbs/bootstrap/issues/19398.
-      color: $input-color;
-      background-color: $input-bg;
-    }
   }
 
   &[multiple],