Don't change screenHeight

[Andrey Pshenkin]

Hi team!

Faced with issue, that when you set screenWidth you also change screenHeight. It causes false positive failures, when you launch test on different devices (with different resolutions)
https://github.com/webdriverio/webdrivercss/blob/22a6b1a85ced0d0050e65623a8e60e4a580e32c4/lib/setScreenWidth.js#L42

Is it possible to change only screenWidth?

Thanks in advance