chore(deps): update mariadb docker tag to v12 (#11)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| mariadb | major | `11.8` -> `12.3` |

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Reviewed-on: https://git.coopcloud.tech/coop-cloud/uptime-kuma/pulls/11
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compose.mariadb.yml

@@ -18,7 +18,7 @@ services:
       - db
 
   db:
-    image: mariadb:11.8
+    image: mariadb:12.3
     environment:
       - MYSQL_ROOT_PASSWORD_FILE=/run/secrets/db_root_password
       - MYSQL_PASSWORD_FILE=/run/secrets/db_password