Reduce the number of CI tests on PR

[montyly]

Everything is still run on a daily basis with cron, but this PR remove unecessary/problematic CI checks on every PR

[elopez]

Can this be done without duplicating the workflow? See e.g. how we do to differenciate the python versions between PRs and other runs

https://github.com/crytic/slither/blob/dfab5ae696a26c2efce9de6cc569d49663af8001/.github/workflows/ci.yml#L28

[montyly]

@elopez : maybe?

I do think that in the long term, we will likely have two different sets of tests for the ones we run on every PR and the ones we run through the cron.

Right now, there is an intersection, but most likely, we don't need that once we have a better testing structure.