[Compose] Update to Redis 6; Update PHP FPM image

docker-compose.yml

@@ -41,7 +41,7 @@ services:
             - mysql
 
     redis-mailcow:
-      image: redis:5-alpine
+      image: redis:6-alpine
       volumes:
         - redis-vol-1:/data/:Z
       restart: always
@@ -103,7 +103,7 @@ services:
             - rspamd
 
     php-fpm-mailcow:
-      image: mailcow/phpfpm:1.75
+      image: mailcow/phpfpm:1.76
       command: "php-fpm -d date.timezone=${TZ} -d expose_php=0"
       depends_on:
         - redis-mailcow