Adds workaround to CI workflow to upgrage pip

[rlratzel]

Description

This PR adds a workaround to the pr.yaml GitHub workflow devcontainer job to upgrade pip. This should allow devcontainer CI jobs that were previously failing due to the older pip version to complete successfully.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[rlratzel]

Closing this since the proper long-term fix to the devcontainers repo for this is in progress.