Update MacOS GHA runners

[flexatone]

What you need to do
(Recommended) If your workflow is architecture agnostic, you can migrate to any of our arm64 labels:

macos-15 or macos-latest
macos-14
macos-14-xlarge
macos-latest-xlarge or macos-15-xlarge

For users that require the x86_64 (Intel) architecture, jobs can be migrated to one of the following labels:

macos-15-intel (new)
macos-14-large
macos-latest-large or macos-15-large