fix: turns legacy command into supported shell

roles/mariadb/tasks/main.yml

@@ -72,9 +72,8 @@
     - "::1"
 
 - name: scripted version of mysql_secure_installation
-  command: "{{ item }}"
+  shell: "{{ item }}"
   args:
-    warn: false
     creates: ~/mysql_secure_installation
   loop:
     - "mysql -e \"DELETE FROM mysql.user WHERE User='';\""