remove mysql

Author: TamaroWalter

.github/workflows/config.json

@@ -2,7 +2,7 @@
   "main-moodle": "MOODLE_500_STABLE",
   "main-php": "8.3",
   "main-db": "pgsql",
-  "dbs": ["pgsql", "mariadb", "mysqli"],
+  "dbs": ["pgsql", "mariadb"],
   "moodle-php": {
     "MOODLE_401_STABLE": ["8.0", "8.1"],
     "MOODLE_404_STABLE": ["8.1", "8.2", "8.3"],