Depreciate integration & example tests on CI for Apple Intel platform

[BradyPlanden]

Feature description

We are currently testing the Intel-based macos-13 platform for integration, examples and unit tests. This platform is expected to be deprecated this coming autumn, with GitHub runners being deprecated alongside.

Since we're also testing the Apple silicon platform via macos-14, I propose that we remove the macos-13 integration and example tests, while keeping the unit tests. This would ensure that we catch potential platform issues with the fast unit tests, while reducing our CI times.

Motivation

No response

Possible implementation

No response

Additional context

No response

[agriyakhetarpal]

Thanks for opening a separate issue. To clarify, here are a few points:

• Intel Macs aren't going anywhere until a few years. They will support macOS 15 and above, and macOS 16 will drop support, thus supporting Silicon-based Macs and later iterations.
• The EOL for macOS 15 will be around three years from the time of the release, based on https://endoflife.date/macos. This means that Intel-based macOS machines will continue to be supported until September 2027.
• For GitHub Actions, the situation is a bit different. I expect that the macos-13 and macos-14 labels to continue to support Intel and ARM like they are now. https://github.com/actions/runner-images#available-images mentions that macos-15 will be ARM-based, and there's no information on how the images will be labelled, or whether the Intel-based Macs will even be supported.

Therefore, it is reasonable to:

• expect that there could be a few users on Intel macOS machines who may file bug reports or ask for support due to PyBaMM's platform-specific behaviours upstream
• for us to mention that we don't actively test those machines due to CI providers' considerations, and are providing support on a best-effort basis