removed old config vars removed in newer MariaDB

Based on https://mariadb.com/kb/en/innodb-system-variables/

Author: deer667

db.mariadb.yml

@@ -5,13 +5,11 @@ services:
       MOODLE_DOCKER_DBTYPE: mariadb
       MOODLE_DOCKER_DBCOLLATION: utf8mb4_bin
   db:
-    image: mariadb:10.2
+    image: mariadb:10
     command: >
               --character-set-server=utf8mb4
               --collation-server=utf8mb4_bin
-              --innodb_file_format=barracuda
               --innodb_file_per_table=On
-              --innodb_large_prefix=On
     environment:
       MYSQL_ROOT_PASSWORD: "m@0dl3ing"
       MYSQL_USER: moodle