get_driver() no longer callable as of Py-TestUI v1.2.0

Calling `get_driver()` in a script works in Py-TestUI v1.1.1, but as of v1.2.0 it now results in `TypeError: 'WebDriver' object is not callable`.

This means that if a project were to upgrade the version of Py-TestUI to use, then all uses of `get_driver()` in scripts would need to be rewritten as `get_driver`.