Drop nav divider mixin

scss/_dropdown.scss

@@ -113,7 +113,10 @@
 
 // Dividers (basically an `<hr>`) within the dropdown
 .dropdown-divider {
-  @include nav-divider($dropdown-divider-bg, $dropdown-divider-margin-y);
+  height: 0;
+  margin: $dropdown-divider-margin-y 0;
+  overflow: hidden;
+  border-top: 1px solid $dropdown-divider-bg;
 }
 
 // Links, buttons, and more within the dropdown menu

scss/_mixins.scss

@@ -27,7 +27,6 @@
 @import "mixins/pagination";
 @import "mixins/lists";
 @import "mixins/list-group";
-@import "mixins/nav-divider";
 @import "mixins/forms";
 @import "mixins/table-row";
 

scss/mixins/_nav-divider.scss

@@ -1,10 +0,0 @@
-// Horizontal dividers
-//
-// Dividers (basically an hr) within dropdowns and nav lists
-
-@mixin nav-divider($color: $nav-divider-color, $margin-y: $nav-divider-margin-y) {
-  height: 0;
-  margin: $margin-y 0;
-  overflow: hidden;
-  border-top: 1px solid $color;
-}

site/content/docs/4.3/migration.md

@@ -23,9 +23,10 @@ See the browser and devices page for details on what is currently supported in B
 Changes to our source Sass files and compiled CSS.
 
 - Removed `hover`, `hover-focus`, `plain-hover-focus`, and `hover-focus-active` mixins. Use regular CSS syntax for these moving forward. [See #28267](https://github.com/twbs/bootstrap/pull/28267).
-- **Todo:** Remove previously deprecated mixins
+- Remove previously deprecated mixins
   - `float()`
   - `form-control-mixin()`
+  - `nav-divider()`
   - `retina-img()`
   - `text-hide()` (also dropped the associated utility class, `.text-hide`)
   - `visibility()`