Update nginx Docker tag to v1.29

This MR contains the following updates:

Package	Update	Change
nginx	minor	1.25 -> 1.29

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testserver/docker_mail/templates/docker-compose.yml

@@ -184,7 +184,7 @@ services:
       - "{{ basedir }}/mailman-web:/opt/mailman-web-data:rw,z"
 
   mailman-nginx:
-    image: nginx:1.25
+    image: nginx:1.28
     restart: always
     depends_on:
       - mailman-web