Publicly allow filtering on identities.providerAccessTokenExpiry

This will allow developers to set up a job to find expired access tokens
so they can refresh them.

src/Appwrite/Utopia/Database/Validator/Queries/Identities.php

@@ -9,6 +9,7 @@ class Identities extends Base
         'provider',
         'providerUid',
         'providerEmail',
+        'providerAccessTokenExpiry',
     ];
 
     /**