[3.11] gh-145098: Use `macos-15-intel` instead of unstable `macos-26-…intel` in `{jit,tail-call}.yml` (GH-148126) (#148138)

* [3.11] gh-145098: Use `macos-15-intel` instead of unstable `macos-26-intel` in `{jit,tail-call}.yml` (GH-148126)
(cherry picked from commit bce96a181350f348560fe0623361f39a6d5c6361)

Co-authored-by: Stan Ulbrych <stan@python.org>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

* macos-26-intel -> macos-15-intel

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Co-authored-by: Stan Ulbrych <stan@python.org>