Add new jdbc.driver.class "com.mysql.cj.jdbc.Driver" to jmeter.properties

[dgetzlaf]

Description

This PR simply adds the new driver class "com.mysql.cj.jdbc.Driver".

Motivation and Context

By providing this new class, this message can be prevented: Loading class com.mysql.jdbc.Driver'. This is deprecated. The new driver class is com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.