Update 01-databases.sql

[diraol]

Two proposed changes here:

1. Update the comment marker from # to -- (SQL standard).
2. From mysql 8 on we can't create a user with the grant command. If you create the user with '<username>'@'localhost' and then try to GRANT .... TO "<username>"@"%" ..., since the "host" is differente (localhost x %) it will try to "create a new user", thus it will fail to start.