document: 'identify flaky tests' link 404

[LeiYangGH]

in page
https://docs.pytest.org/en/stable/explanation/flaky.html
there's link identify flaky tests
currently return 404.

[Zac-HD]

Given that the page is gone, I think we should just delete that whole "CI tools that rerun on failure" section.

[Zoorken]

The commit I prepared could be made into a pull request if the section still adds value.

I follow the preparing-pull-requests when making the commit

Please guide me if I missed a step

[nicoddemus]

@Zoorken great that you found the original link, feel free to open a PR with that commit!

[SauravMaheshkar]

Shouldn't this issue be closed after #10301 ?