FEATURE: allow group membership to unmute categories and tags

For sites that are configured to mute some or all categories and tags
for users by default, groups can now be configured to set members'
notification level to normal from the group manage UI.

app/models/group.rb

@@ -765,7 +765,7 @@ class Group < ActiveRecord::Base
     flair_icon.presence || flair_upload&.short_path
   end
 
-  [:muted, :tracking, :watching, :watching_first_post].each do |level|
+  [:muted, :regular, :tracking, :watching, :watching_first_post].each do |level|
     define_method("#{level}_category_ids=") do |category_ids|
       @category_notifications ||= {}
       @category_notifications[level] = category_ids