Do not send alias events when creating / upgrading a room (#6941)

Stop emitting room alias update events during room creation/upgrade.

synapse/handlers/directory.py

@@ -14,6 +14,7 @@
 # limitations under the License.
 
 
+import collections
 import logging
 import string
 from typing import List
@@ -282,22 +283,6 @@ class DirectoryHandler(BaseHandler):
                 Codes.NOT_FOUND,
             )
 
-    @defer.inlineCallbacks
-    def send_room_alias_update_event(self, requester, room_id):
-        aliases = yield self.store.get_aliases_for_room(room_id)
-
-        yield self.event_creation_handler.create_and_send_nonmember_event(
-            requester,
-            {
-                "type": EventTypes.Aliases,
-                "state_key": self.hs.hostname,
-                "room_id": room_id,
-                "sender": requester.user.to_string(),
-                "content": {"aliases": aliases},
-            },
-            ratelimit=False,
-        )
-
     @defer.inlineCallbacks
     def _update_canonical_alias(self, requester, user_id, room_id, room_alias):
         """
@@ -326,7 +311,7 @@ class DirectoryHandler(BaseHandler):
         alt_aliases = content.pop("alt_aliases", None)
         # If the aliases are not a list (or not found) do not attempt to modify
         # the list.
-        if isinstance(alt_aliases, list):
+        if isinstance(alt_aliases, collections.Sequence):
             send_update = True
             alt_aliases = [alias for alias in alt_aliases if alias != alias_str]
             if alt_aliases: