DEPR: Deprecating Function Arguments
When we want to deprecate and remove arguments, our general methodology has been to issue the deprecation warning ONLY when a non-default argument has been passed in.

However, @jorisvandenbossche pointed out in #17820 that this warnings framework does not take into account situations where the user EXPLICITLY passes in the default argument.  Thus, we risk breaking downstream code in that case.

An alternative method would be to *change* the default argument (to some dummy) that we can use to catch this argument when passed in with the current accepted values.

While I have not seen this case emerge (patching is relatively painless, which might be why we haven't seen this issue on our tracker), I think it's worthwhile considering as we move forward with parameter deprecations + adjusting previous ones.