fix: undo translation of 'restart' keyword for docker-compose (#385)

docs/post_installation/firststeps-disable_ipv6.de.md

@@ -39,7 +39,7 @@ services:
 
     ipv6nat-mailcow:
       image: bash:latest
-      neustart: "no"
+      restart: "no"
       entrypoint: ["echo", "ipv6nat disabled in compose.override.yml"]
 ```
 
@@ -80,4 +80,4 @@ Starten Sie Postfix neu:
 
 ```
 docker-compose restart postfix-mailcow
-```
+```