Resize browser at Sauce Labs to maximum supported size

Paired with Paired with Amire80 <amir.aharoni@mail.huji.ac.il>

For some reason browsers at Sauce Labs do not use the entire screen.
Example:

https://saucelabs.com/jobs/f2eb8b87ebc147f2bc621ea38cb05a1a

Picking OS screen size is at the moment supported for Windows only, so
we are resizing the browser instead.

Documentation:

https://saucelabs.com/docs/additional-config#screen-res

Change-Id: I3cb314202db7aa102069ffea19a3bde31a7b83fb