Changed scroll to auto for some UI elements. (#20294)

Addition to: Show scrollbar when necessary #20142
Fixes the "empty" scrollbars with Firefox.

web_src/less/features/gitgraph.less

@@ -1,5 +1,5 @@
 #git-graph-container {
-  overflow-x: scroll;
+  overflow-x: auto;
   width: 100%;
   min-height: 350px;