Fix Docker cache in Actions workflow

[No767]

Summary

This PR just fixes the cache-to key in the docker build workflow.

Types of changes

What types of changes does your code introduce to Rodhaj Put an x in the boxes that apply

• [x] Bugfix (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 not work as expected)
• [ ] Documentation Update (Updates to README.md, the documentation, etc)
• [ ] Other (if none of the other choices apply)

Checklist

Put an x in the boxes that apply

• [ ] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes. (if appropriate)
• [x] All workflows (except pre-commit.ci) pass with my new changes
• [x] This PR does not address a duplicate issue or PR

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud