Feature and motivation

I initially proposed changing to the new Headless (#11099), but @jimevans convinced us we should just deprecate the method entirely and have people choose what they want in the args.

This change will require writing a blog post explaining the change and advertising the new Chrome method, and adding examples to the documentation.

Usage example

Deprecate this:

options = Selenium::WebDriver::Options.chrome
options.headless!

and advertise this:

options = Selenium::WebDriver::Options.chrome(args: ['--headless=chrome'])