Apply utilities in docs styles (#30866)

* docs(theming): apply utilities where possible

* Update docs-sidebar.html

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

site/assets/scss/_sidebar.scss

@@ -15,13 +15,10 @@
   }
 
   a {
-    display: inline-flex;
-    align-items: center;
     padding: .1875rem .5rem;
     margin-top: .125rem;
     color: rgba($black, .65);
     text-decoration: if($link-decoration == none, null, none);
-    @include border-radius(.25rem);
 
     &:hover,
     &:focus {
@@ -57,7 +54,6 @@
     // Adjust font size and font weights in submenu
     + ul {
       @include font-size(.875rem);
-      font-weight: 400;
     }
   }