fix broken avatar checks when server_name contains a port

changelog.d/13927.bugfix

@@ -0,0 +1 @@
+Fixes check_avatar_size_and_mime_type() to successfully update avatars on homeservers running on non-default ports which were mistakenly treated as remote homeserver while validating the avatar's size and mime type. Contributed by @ashfame.

synapse/handlers/profile.py

@@ -307,7 +307,11 @@ async def check_avatar_size_and_mime_type(self, mxc: str) -> bool:
         if not self.max_avatar_size and not self.allowed_avatar_mimetypes:
             return True
 
-        server_name, _, media_id = parse_and_validate_mxc_uri(mxc)
+        host, port, media_id = parse_and_validate_mxc_uri(mxc)
+        if port is not None:
+            server_name = host + ":" + str(port)
+        else:
+            server_name = host
 
         if server_name == self.server_name:
             media_info = await self.store.get_local_media(media_id)