Revert "Merge branch 'document-nocov-for-undercover' into 'master'"

What does this MR do and why?

I will like to revert this, as I now think adding :nocov: to workaround undercover is an anti-pattern.

1. Test coverage is a Performance Indicator for Backend engineers. Adding :nocov: skews the stats
2. From the originating discussion in !75001 (comment 845696090), undercover actually caught a legitimate issue (the method was defined outside the class). So we didn't use :nocov: there in the end.
3. #357381 (closed) was another issue where undercover legitimately showed an issue (specs did not run on CI) but we worked around it with :nocov: incorrectly.
4. Given we have the pipeline:skip-undercoverage label, I think that is enough.

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