Merge branch 'fix-sticky-tabs-position' into 'master'

Update height of $mr-tabs-height

See merge request gitlab-org/gitlab-ce!29619

app/assets/stylesheets/framework/variables.scss

@@ -823,7 +823,7 @@ $issues-analytics-popover-boarder-color: rgba(0, 0, 0, 0.15);
 /*
 Merge Requests
 */
-$mr-tabs-height: 51px;
+$mr-tabs-height: 48px;
 $mr-version-controls-height: 56px;
 
 /*