Undefined name: driver --> self.driver

[cclauss]

driver is an undefined name in this context which will raise NameError at runtime so this PR recommends using self.driver which is already used previously on this same line of code.

flake8 testing of https://github.com/ThoughtfulDev/EagleEye on Python 3.8.0

$ flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics

233./grabber/google.py:56:50: F821 undefined name 'driver'
234                    self.driver.switch_to.window(driver.window_handles[1])
235                                                 ^
2361     F821 undefined name 'driver'
2371

https://flake8.pycqa.org/en/latest/user/error-codes.html

On the flake8 test selection, this PR does not focus on "style violations" (the majority of flake8 error codes that psf/black can autocorrect). Instead these tests are focus on runtime safety and correctness:

• E9 tests are about Python syntax errors usually raised because flake8 can not build an Abstract Syntax Tree (AST). Often these issues are a sign of unused code or code that has not been ported to Python 3. These would be compile-time errors in a compiled language but in a dynamic language like Python they result in the script halting/crashing on the user.
• F63 tests are usually about the confusion between identity and equality in Python. Use ==/!= to compare str, bytes, and int literals is the classic case. These are areas where a == b is True but a is b is False (or vice versa). Python >= 3.8 will raise SyntaxWarnings on these instances.
• F7 tests logic errors and syntax errors in type hints
• F82 tests are almost always undefined names which are usually a sign of a typo, missing imports, or code that has not been ported to Python 3. These also would be compile-time errors in a compiled language but in Python a NameError is raised which will halt/crash the script on the user.