Hi,
I've found this link : The "test" Database and Security that explain the "test" database (I know that it's oracle -mysql-) but I think that is probably the truth for MariaDB too. So, is this the function for the user "Any" too ?
No. The entry means that anyone from anywhere can connect to the database and use it. Check the detailed permissions, but in general, this is not correct. My suggestion is to make a backup of the table, then remove then entry and check that things are still all working.