chore(deps): update axllent/mailpit docker tag to v1.28.1

Author: renovate[bot]

stack/docker-compose.yml

@@ -76,7 +76,7 @@ services:
 
   # === Mail ===
   mailpit:
-    image: axllent/mailpit:v1.21.8@sha256:81370195cd4a0eab9604d17c2617a7525b0486f9365555253b6c5376c6350f1a
+    image: axllent/mailpit:v1.28.1@sha256:ff948a98fd2d16d717f7fd8f2a4ea66a8735d67ad3f7996497670b0fbf1f9797
     ports:
       - '1025:1025' # SMTP Server
       - '8025:8025' # UI