ci: use macos-15-intel runner

[xtqqczze]

seems unnecessary to use macos-15-large just for x86_64 support

Larger runners are not eligible for the use of included minutes on private repositories. For both private and public repositories, when larger runners are in use, they will always be billed at the per-minute rate.

https://docs.github.com/en/actions/concepts/runners/larger-runners#billing

Stacked on #2001

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