Update mariadb Docker tag to v12 (#298)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

docker-compose.yaml

@@ -75,7 +75,7 @@ services:
       retries: 5
 
   mariadb:
-    image: mariadb:11.8
+    image: mariadb:12.0
     environment:
       MYSQL_ROOT_PASSWORD: "stanis"
       MYSQL_DATABASE: "backend"