Unpin pester install version in run-pester-tests.yml once the version on the Windows images is 5.6.0 or higher

[JimSuplizio]

This is a known issue documented on the pester release for 5.6.0

Right now, the devops Windows images have pester 5.5.0. The release of 5.6.0 on 6/5/2024 has different signing. This causes the install the fail on Windows because the signing is different between the two.

When the version on the Windows machines is 5.6.0 we can revert the pinning of the version in run-pester-tests.yml