Docs: add Vale test for warning-level substitutions

What does this MR do?

There are some word choices we want to disallow in the future, but the cleanup to get rid of them requires more time than we can spend on the entire docset at this time. A moderate approach would be to create a warning-level (as opposed to error-level) substitution test for these word pairs, so we can start cleaning out the informal versions of these words over time. If we focus on cleaning up all instances of a word and occurrences hit zero, we can move a word from the warnings file to the errors file.

Related issues

Closes #211983 (closed)

Author's checklist (required)

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Review checklist

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