[jdk21u-dev] RFR: 8369226: GHA: Switch to MacOS 15

[Volker Simonis]

On Fri, 24 Oct 2025 11:47:15 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Switching to MacOS 15 ahead of brownouts and deprecations.
> 
> Additional testing:
>  - [x] GHA

Looks good, thanks!

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Marked as reviewed by simonis (Reviewer).

PR Review: https://git.openjdk.org/jdk21u-dev/pull/2389#pullrequestreview-3377347954