operator-sdk: build with go@1.21

[stefanb]

Moved from

• go@1.21 1.21.7 (new formula) #162713

as a follow-up

Related:

• go 1.22.0 #157782

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• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 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 HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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[chenrui333]

@stefanb I think the tests are failing for both as well?

[chenrui333]

relates to operator-framework/operator-sdk#6644

[github-actions]

@chenrui333 has requested bottles to be published to this PR.