Update maxking/mailman-web Docker tag to v0.5

This MR contains the following updates:

Package	Update	Change
maxking/mailman-web	minor	0.4 -> 0.5

---

Configuration

Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

Automerge: Disabled by config. Please merge this manually once you are satisfied.

Rebasing: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Renovate Bot.

testserver/docker_mail/templates/docker-compose.yml

@@ -175,7 +175,7 @@ services:
       - "{{ basedir }}/mailman-core:/opt/mailman:rw,z"
 
   mailman-web:
-    image: maxking/mailman-web:0.4
+    image: maxking/mailman-web:0.5
     restart: always
     env_file: mailman.env
     depends_on: