fix path in workflows for restoring openmc shared library

[yardasol]

Summary of changes

This PR fixes the broken Test SaltProc workflow caused by an incorrect path in the script that copies the OpenMC shared libraries to a cache-able directory. The incorrect path caused the following error in the CI:

+ cp -r /usr/local/lib/x86_64-linux-gnu/ openmc_src/lib/.
cp: cannot stat '/usr/local/lib/x86_64-linux-gnu/': No such file or directory
Error: Process completed with exit code 1.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Required for Merging

• [x] I have read the CONTRIBUTING document.

• [x] My code follows the code style of this project.

• [ ] My change requires a change to the documentation.

  • [ ] I have updated the documentation accordingly.

• [ ] My change is a source code change

  • [ ] I have added/modified tests to cover my changes
  • [ ] I have explained why my change does not require new/modified tests

• [ ] My change is a user-facing change

  • [ ] I have recorded my changes in the changelog for the upcoming release

• [x] My change is exclusively related to the repository (e.g. GitHub actions workflows, PR/issue templates, etc.)

  • [x] I have verified or justified that my change will work as intended.
  • Installing from source
  • Restoring from cache

• [x] All new and existing tests passed.

  • [x] CI tests pass
  • [x] Local tests pass (including Serpent2 integration tests)

    Associated Issues and PRs

• Issue: none

Associated Developers

• Dev: @munkm

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