Update examples to use the newer CF Turnstile selector

[mdmintz]

Update examples to use the newer CF Turnstile selector

The Cloudflare Turnstile checkbox selector changed from span.mark to just span.
I've already updated the tests for it: e693775

This is not surprising, considering that they are watching me:
https://www.youtube.com/watch?v=2pTpBtaE7SQ&t=1907s

People should be aware that websites can change, which causes CSS Selectors to change too.

Thankfully, no SeleniumBase changes were needed this time, unlike last time: #2626

In case there's any confusion, this is all you need to do:

...and that should solve the issue!

[mdmintz]

If you need to click a CF CAPTCHA checkbox on Linux now, upgrade to 4.28.0 (or newer) and use driver.uc_gui_handle_cf(). (The solution uses pyautogui)