Update mariadb Docker tag to v12

Author: renovate[bot]

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
         python-version: ["3.10", "3.11", "3.12"]
     services:
       mariadb:
-        image: mariadb:11.7.2 # released 2024-05-06
+        image: mariadb:12.1.2 # released 2024-05-06
         # Pulls image from DockerHub
         # Docker images: https://hub.docker.com/_/mariadb
         # Previous version(s):