RFR: 2391: Update .github/workflows/ci.yml

[Zhao Song]

On Wed, 16 Oct 2024 22:01:27 GMT, Zhao Song <zsong at openjdk.org> wrote:

> Today I received an email from Github and in the email, GitHub says they are going to remove macOS 12 runner image soon.
> We should update our configuration since we are using macOS 12 runner right now.

Thank you for the review!

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PR Comment: https://git.openjdk.org/skara/pull/1691#issuecomment-2418101065