Declare preference for "cherry-pick" and test it

What does this MR do?

Yesterday in Slack, Hiru brought up an inconsistency she spotted in the nav: cherry pick in one place, and cherry-pick in another. I checked the Git documentation for git cherry-pick, and they prefer cherry-pick in natural language: https://git-scm.com/docs/git-cherry-pick

This MR should wrap up the problem, by adding an entry to the word list, and adding it to a substitution test. The full slate of MRs done so far:

• Fix the nav: gitlab-docs!5339 (merged)
• Fix in-page usage: !179858 (merged)
• (this MR) Add word-list guidance and a test

(@brendan777, thanks for the tag-team! Hiru found that problem in the last few minutes of my day, and I knew if I didn't tag you in the Slack thread right then, I ran the risk of forgetting to fix this.)

Related issues

Related to Inconsistent use of 'cherry-pick' versus 'cherr... (gitlab-docs#1849 - closed)

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