Update macOS version in CI workflow

[wsmoses]

No description provided.

[github-actions]

Benchmark Results

	main	49ff722...	main / 49ff722...
basics/overhead	5.26 ± 0.01 ns	5.56 ± 0.92 ns	0.946 ± 0.16
time_to_load	1.26 ± 0.005 s	1.27 ± 0.019 s	0.997 ± 0.016

Benchmark Plots

A plot of the benchmark results has been uploaded as an artifact at https://github.com/EnzymeAD/Enzyme.jl/actions/runs/17654183883/artifacts/3989414660.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.93%. Comparing base (701f5f9) to head (49ff722).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2563   +/-   ##
=======================================
  Coverage   74.93%   74.93%           
=======================================
  Files          56       56           
  Lines       17445    17445           
=======================================
  Hits        13073    13073           
  Misses       4372     4372           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[giordano]

Uhm, this was changed in #2273 because jobs were timing out. Using x86_64 builds of Julia on apple silicon via Rosetta is very unsupported and error-prone, and also github won't allow it anymore at some point: https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/#notice-of-macos-x86_64-intel-architecture-deprecation.

I think the best path forward is to simply use the native architecture everywhere in all the jobs, I'll open a pull request to that effect in a few minutes.