cleanup: Remove unneeded escapes in regex

. and ) lose their special meaning in character sets, so they don't
need escaping. The same applies to - when it isn't part of a range.

Spotted by eslint.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/607

js/ui/messageTray.js

@@ -248,7 +248,7 @@ class NotificationApplicationPolicy extends NotificationPolicy {
     _canonicalizeId(id) {
         // Keys are restricted to lowercase alphanumeric characters and dash,
         // and two dashes cannot be in succession
-        return id.toLowerCase().replace(/[^a-z0-9\-]/g, '-').replace(/--+/g, '-');
+        return id.toLowerCase().replace(/[^a-z0-9-]/g, '-').replace(/--+/g, '-');
     }
 
     get enable() {