Fixes a bug where very tall files would be appear incorrectly

This issue appears with virtual scrolling enabled
and there is a large diff on the page.

app/assets/stylesheets/framework/diffs.scss

@@ -1192,5 +1192,5 @@ table.code {
 // Note: Prevents tall files from appearing above sticky tabs
 .diffs .vue-recycle-scroller__item-view > div:not(.active) {
   position: absolute;
-  top: 100vh;
+  bottom: 100vh;
 }