Test PRs on a subset of the workflow matrix #149
Description
The PRs are being tested on 3 OSs and 3 Julia versions. Some combinations are pretty slow to it might be better to remove them from the PR test.
The main disadvantage is that we might approve PRs that fail for some combination, but I think itis fine since we only release working versions, so there is time to fix or revert the PR before release.
Related: https://github.com/abelsiqueira/COPIERTemplate.jl/issues/105