Tests: Use global no_throttling_everywhere fixture (#701)

Instead of needing to individually disable throttling on a per-plugin
basis, this fixture takes care of all notifiers in `NOTIFY_MODULE_MAP`
automatically. With `autouse=True`, there is no need to activate it
manually.

test/test_plugin_ses.py

@@ -377,8 +377,6 @@ def test_plugin_ses_attachments(mock_post):
     NotifySES() Attachment Checks
 
     """
-    # Disable Throttling to speed testing
-    NotifySES.request_rate_per_sec = 0
 
     # Prepare Mock return object
     response = mock.Mock()