disable gravatar in test (#32529)

When running e2e tests on flaky networks, gravatar can cause a timeout
and test failures. Turn off, and populate avatars on e2e test suite run
to make them reliable.

Author: bohde

models/fixtures/system_setting.yml

@@ -1,7 +1,7 @@
 -
   id: 1
   setting_key: 'picture.disable_gravatar'
-  setting_value: 'false'
+  setting_value: 'true'
   version: 1
   created: 1653533198
   updated: 1653533198