user events: make all events visible to moderators.

Allow moderators to see all events on the /user_events page. Before only
admins could see when a user changed their email, changed their
password, or had a failed login attempt. Now moderators can see these
events too.

Filtering these events out made the /user_actions page slower, and it
wasn't really necessary since merely knowing that a user changed their
email or password isn't that much more sensitive than knowing when they
logged in or out.

app/models/user_event.rb

@@ -24,10 +24,10 @@ class UserEvent < ApplicationRecord
   delegate :country, :city, :is_proxy?, to: :ip_geolocation, allow_nil: true
 
   def self.visible(user)
-    if user.is_admin?
+    if user.is_moderator?
       all
-    elsif user.is_moderator?
-      where(category: [:login, :logout, :user_creation]).or(where(user: user))
+    elsif user.is_anonymous?
+      none
     else
       where(user: user)
     end