Fix intermittent Selenium::WebDriver::Error::UnknownError

[DavidBiddle]

What problem does this pull request solve?

Trello card:

We've had a longstanding issue with our Capybara tests intermittently failing with message:

Selenium::WebDriver::Error::UnknownError:
       unknown error: unhandled inspector error: {"code":-32000,"message":"Node with given id does not belong to the document"}

when using recent versions of Chrome.

This is an instance of teamcapybara/capybara#2800

Previously we resolved this by pinning our CI to an older version of Chrome, then in some repos including this one we added a patch to retry tests when they hit this error.

Subsequently the root cause was identified on the Capybara issue (I believe thanks to an explanation of the error and a test case from @lfdebrux 🙌 ).

This PR:

• adds a flag to the Chrome options which should resolve the issue
• removes the retry patch, since it should no longer be needed

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• Are there all the unit tests needed?
• Do the end to end tests need updating before these changes will pass?
• Has all relevant documentation been updated?

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[DavidBiddle]

I've tested this locally by running the content of this feature test 300 times without seeing the error (200 headless, 100 with the GUI)