Revert "Issue #3420974 by andypost, quietone: Add testing wtih Maria DB 10.6"

This reverts commit db681552.

.gitlab-ci.yml

@@ -210,12 +210,6 @@ default:
     _TARGET_PHP: "8.3"
     _TARGET_DB: "sqlite-3"
 
-'PHP 8.3 MariaDB 10.6':
-  <<: [ *default-stage, *run-on-mr ]
-  variables:
-    _TARGET_PHP: "8.3"
-    _TARGET_DB: "mariadb-10.6"
-
 'PHP 8.1 MariaDB 10.3.22':
   <<: [ *default-stage, *run-on-mr ]
   variables: