[CI] Upgrade macos-13 to macos-latest

[cvanaret]

The macOS 13 runner image will be retired by December 4th, 2025. This deprecation includes the following labels:

• macos-13
• macos-13-large
• macos-13-xlarge

[imciner2]

The macos-latest runner image is an aarch64 runner image, but it looks like it is in the x64 architecture block here. This means you will be requesting the x64 Julia version on the arm64 machine, so it goes through the emulation layer - this then triggers the new warning added in setup-julia: julia-actions/setup-julia#300. There was a discussion on the Julia Slack last month actually about running the x64 version on arm64 in CI having problems with artifacts loading properly. I would suggest that if you want an x64 architecture for macOS here, use the macos-15-intel runner image for that.

[amontoison]

I tried it and I can't install the Fortran compiler for CUTEst.jl. I don't know why the system is unable to find gfortran. I just changed macos-13 into macos15-intel.