25.4.8 sticky-sidebar overlap fix

refined-github/refined-github#8445

Author: fregante

style/25.4.8.css

@@ -0,0 +1,4 @@
+/* z-index fight https://github.com/refined-github/refined-github/issues/8445 */
+.rgh-sticky-sidebar {
+	z-index: unset !important;
+}