Fix sending notifications that aren't ours, such as the password reset email

Summary: Didn't realize the password reset message went through the notification system.

Test Plan:
- Attempt to reset a password
- Ensure it goes through
- Cause some other notifications
- Ensure they go through

Reviewers: sethetter

Reviewed By: sethetter

Differential Revision: https://phabricator.opengovfoundation.org/D196

Author: doshitan

app/Listeners/ShouldSendNotification.php

@@ -33,6 +33,10 @@ public function handle(NotificationSending $event)
         $recipient = $event->notifiable;
         $notification = $event->notification;
 
+        if (!($notification instanceof \App\Contracts\Notification)) {
+            return;
+        }
+
         // determine if the recipient *is allowed to receive* notifications from
         // this kind of event, i.e., if the event is not in the set of valid
         // notifications for the recipient, then skip it