Update 2 to 4 cores used in tests on GitHub Actions runners

[williamfgc]

Proposed changes

GitHub Actions now provides 4 cores in free runners on Linux and macOS 13
This PR adds more test concurrency from 2 to 4

What type(s) of changes does this code introduce?

Delete the items that do not apply

• Testing changes (e.g. new unit/integration/performance tests)

Does this introduce a breaking change?

• No

What systems has this change been tested on?

N/A, must pass CI

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• Yes. This PR is up to date with current the current state of 'develop'
• No. Code added or changed in the PR has been clang-formatted
• No. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• No. Documentation has been added (if appropriate)

[ye-luo]

Test this please

[prckent]

Thanks William