Don't explain SQL in mysql cheat

`mysql` refers to the command line client that comes with [MySQL](https://dev.mysql.com/doc/refman/8.0/en/mysql.html) or [MariaDB](https://mariadb.com/kb/en/mysql-command-line-client/).

This cheat shouldn't show SQL examples. `psql` cheat doesn't, and I find it much cleaner.
