RFR: 1943: Update .github/workflows/ci.yml to fix GHA [v2]

[Zhao Song]

On Wed, 14 Jun 2023 17:17:26 GMT, Zhao Song <zsong at openjdk.org> wrote:

>> Since last month, the GitHub Action for running tests on macOS has been failing consistently, and the test job always failed due to time out. It seems like that GitHub no longer supports tests on macOS-10.15, so we need to update the configuration.
>
> Zhao Song has updated the pull request incrementally with one additional commit since the last revision:
> 
>   change the platform for macos

Thanks for the review!

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PR Comment: https://git.openjdk.org/skara/pull/1530#issuecomment-1591797626