Add deprecate reason

[Rylan12]

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

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Add because: argument to deprecate! in formulae.

Supplement to #60321

CC: @MikeMcQuaid

[Rylan12]

@MikeMcQuaid now that the brew PR fixing the issue has been merged this should be good to go. I've rebased and it now passes the style checks.

[MikeMcQuaid]

Thanks again @Rylan12!