Altered group name not applied/updated for rejoined members

[gerryfrancis]

• Operating System (Linux/Mac/Windows/iOS/Android):
  Android 15.

• Delta Chat Version:
  1.50.4 (beta).

• Expected behavior:
  After a former member has rejoined a group, a possibly altered group name shall be applied/updated at the client.

• Actual behavior:
  After a former member has rejoined a group, a possibly altered group name is not applied/updated at the client.

• Steps to reproduce the problem:
  Assuming that Alice and Bob are members of a group:
  -- Bob leaves the group.
  -- Alice renames the group.
  -- Bob rejoins the group. (Result: The altered group name does not show up for Bob, the former name remains.)

• Screenshots:
  N/A.

• Logs:
  N/A.

• Credits:
  adb, Raiden.