Fix Firefox E2E CI gate

It seems that something has got broken recently, so we had to disable these E2E tests on Firefox.
Was it Firefox 131.0, or anything in SeleniumBase? Or simply an issue with a new default GitHub Actions Ubuntu image?

You can find an example of a failed CI run here: https://github.com/falconry/falcon/actions/runs/11254279330/job/31291767229
```
__________________________________ test_chat ___________________________________

browser = .BaseClass testMethod=base_method>
clear_log = ._impl at 0x7f7f0a27bc40>

def test_chat(browser, clear_log):
browser.slow_click('#button1')
> browser.assert_text('Hello, WS1!', 'div.ws1', timeout=5)

e2e-tests/test_e2e.py:41:

<...>

exception =
message = 'Element {div.ws1} was not present after 5 seconds!'

def timeout_exception(exception, message):
exc, msg = shared_utils.format_exc(exception, message)
> raise exc(msg)
E seleniumbase.common.exceptions.NoSuchElementException: Message:
E Element {div.ws1} was not present after 5 seconds!
```

Start with the failed CI run and e2e-tests/test_e2e.py at test_chat, especially the Firefox failure around line 41. Reproduce the missing div.ws1 failure and compare the Firefox, SeleniumBase, and GitHub Actions environment involved. Done means the Firefox E2E tests pass reliably and the CI gate can be re-enabled.

Written by the indexing model from the issue text.