Issue #3238663: Use Maria DB 10.5.12 for Single Instance CFn template.

cfn/nested/database/template.yaml

@@ -133,8 +133,8 @@ Resources:
       DBInstanceClass: !Ref RDSInstanceType
       DBName: !Ref DatabaseName
       DBSubnetGroupName: !Ref DbSubnetGroup
-      Engine: MySQL
-      EngineVersion: 5.7.34
+      Engine: MariaDB
+      EngineVersion: 10.5.12
       MasterUsername: !Ref MySQLUserName
       MasterUserPassword: !Ref MySQLPassword
       Port: '3306'