Fix thin scrollbar being applied to entire site (internetarchive#8855)

* Fix thin scrollbar being applied to entire site

This css was leaking and applying to the entire site. We don't want thin scrollbars everywhere.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

static/css/components/tagging-menu.less

@@ -52,24 +52,24 @@
 // Menu option containers:
 .selection-container {
   height: 266px;
-  overflow-y: scroll;
+  overflow-y: auto;
 
   .subjects-search-results,
   .selected-tag-subjects {
     padding: 0 5px;
   }
-}
 
-::-webkit-scrollbar {
-  -webkit-appearance: none;
-  background-color: @lighter-grey;
-  width: 5px;
-}
+  &::-webkit-scrollbar {
+    -webkit-appearance: none;
+    background-color: @lighter-grey;
+    width: 5px;
+  }
 
-::-webkit-scrollbar-thumb {
-  border-radius: 4px;
-  background-color: @grey;
-  -webkit-box-shadow: 0 0 1px @grey;
+  &::-webkit-scrollbar-thumb {
+    border-radius: 4px;
+    background-color: @grey;
+    -webkit-box-shadow: 0 0 1px @grey;
+  }
 }
 
 .search-subject-row {