chore(deps): update axllent/mailpit docker tag to v1.28.3

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:v1.28.3@sha256:27cfb8893806ed676042a00f4db70325a0d57cc5217349d210b6dd903e1a7e67
     ports:
       - '1025:1025' # SMTP Server
       - '8025:8025' # UI