Unused Firefox v9 test

[MikeMcC399]

Current situation

• After determining through issue "Still waiting to connect to Firefox" Firefox103 | Ubuntu 20.04 | Cypress 9.50.0 cypress#23215 that flaky Firefox testing in Cypress v9 was not going to be resolved, PR Skip Firefox test using Cypress v9 to resolve flaky tests #660, merged on Dec 15, 2022, caused the .github/workflows/example-firefox.yml to skip the Firefox test for v9, leaving all the corresponding code otherwise untouched.

• This causes a skipped test to be reported for every push to master and for every pull_request trigger.

Suggested change

1. Remove the firefox-v9 job from .github/workflows/example-firefox.yml, leaving a comment explaining about the issue preventing reliable tests with Mozilla Firefox using Cypress v9.
2. Remove the unused directory examples/v9/firefox

Benefit

• The continually logged skipped job firefox-v9 showing in actions/workflows/example-firefox.yml and showing in any open PR checklists will no longer appear
• unused code is cleaned up

[MikeMcC399]

• PR Remove firefox v9 example #741 submitted to resolve this issue