Fix double scrollbar issues

app/assets/stylesheets/framework/gitlab-theme.scss

@@ -118,3 +118,19 @@ body {
     @include gitlab-theme(#9988CC, $theme-violet, #443366, #332255);
   }
 }
+
+::-webkit-scrollbar{
+  width: 3px;
+}
+
+::-webkit-scrollbar-thumb{
+  background-color:$theme-charcoal; border-radius: 0;
+}
+
+::-webkit-scrollbar-thumb:hover{
+  background-color:$theme-charcoal;
+}
+
+::-webkit-scrollbar-track{
+  background-color:#FFF;
+}
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