Fixed: libmysqlclient18 package not available for Ubuntu 16.04

Quote from i-MSCP Github (1.3.x)

Code

1. Fixed: libmysqlclient18 package not available for Ubuntu 16.04
2. [ci skip]

Source: https://github.com/i-MSCP/imsc…113f5fd923b770d7d891f7f6a