Remove unused css

Many of these classes don't exist nested under .navbar-search.  Additionally we don't need the sibling selector as there is only one .navbar-search on the page.

Author: jcoyne

app/assets/stylesheets/arclight/modules/mastheads.scss

@@ -1,9 +1,13 @@
 .navbar-search {
+  border-bottom: $default-border-styling;
+  border-top: $default-border-styling;
+  margin-bottom: ($spacer * 0.5);
   z-index: 10;
+
   .search-query-form {
-    max-width: 100% !important;   // work around blacklight styles
+    max-width: 100% !important; // work around blacklight styles
     display: flex;
-    gap: .5rem;
+    gap: 0.5rem;
 
     // wrap collection dropdown onto its own line on smaller screens
     @include media-breakpoint-down(md) {
@@ -22,7 +26,10 @@
 }
 
 .al-masthead {
-  h1, .h1 {
+  --al-mastead-active-link-color: var(--bs-gray-700);
+
+  h1,
+  .h1 {
     display: block;
     font-size: $h2-font-size;
     margin: 0;
@@ -33,31 +40,8 @@
     flex-direction: row;
     font-weight: 700;
 
-  .active a {
-      color: $gray-700;
-    }
-  }
-
-  + .navbar-search {
-    border-bottom: $default-border-styling;
-    border-top: $default-border-styling;
-    margin-bottom: ($spacer * 0.5);
-
-    a {
-      font-weight: $font-weight-bold;
-    }
-
     .active a {
-      color: $gray-700;
-    }
-
-    .navbar-toggler {
-      background-color: $white;
-      border: $default-border-styling;
-    }
-
-    .navbar-toggler-icon {
-      background-image: $navbar-light-toggler-icon-bg;
+      color: var(--al-mastead-active-link-color);
     }
   }
 
@@ -66,8 +50,7 @@
       justify-content: center !important;
     }
 
-    h1,
-    + .navbar-search {
+    h1 {
       text-align: center;
     }
   }