fix(ci): migrate off the retired macos-13 runner (#5711)
`macos-13` runner is being retired, and jobs using it are beginning to
fail with these errors:
```
The macOS-13 based runner images are now retired. For more details, see https://github.com/actions/runner-images/issues/13046.
The macOS-13 based runner images are being deprecated, consider switching to macOS-15 (macos-15-intel) or macOS 15 arm64 (macos-latest) instead. For more details see https://github.com/actions/runner-images/issues/13046
```
(for example, see
https://github.com/prisma/prisma-engines/actions/runs/20172373777/job/57911402339).
This commit migrates our macOS CI jobs to use the `macos-15` and
`macos-15-intel` runners.
