admin screen: override fill attribute of paths

When an svg has a fill attribute directly on the path, we need more
specifity to override it.

lib/tpl/dokuwiki/css/_admin.less

@@ -34,6 +34,9 @@
                         height: 1.5em;
                         fill: @ini_link;
                         display: inline-block;
+                        path {
+                            fill: @ini_link;
+                        }
                     }
                 }