Return to the correct original git state

[m-chrzan]

Description

The version check script checks out contracts from prior git refs, then should return to the original state. We tried to use - to return to the previously checked out ref, but this only works when checking out the entire ref, whereas here we were using it to checkout only a specific files (... -- contracts/). This was resulting in an unexpected git tree after the script ran. This PR fixes this behavior in the check-versions.sh script, and release-lib.sh, on which it depends.

Tested

Ran check-versions.sh multiple times on different branches while investigating #9753, after these fixes, ended with clean git tree after each run.

Related issues

• Fixes #9323