In case you don't recognize the syntax, this is HCL and was the system in use before it was changed to YML. This change seems to have been (partially) a result of being purchased by Microsoft since the HCL version ran on Google Cloud while the new one used Azure instances.
Question: What did,"<a href="https://api.github.com/repos/actions/docker/tarball/76ff57a" rel="nofollow">https://api.github.com/repos/actions/docker/tarball/76ff57a</a>" had anything to do with the OPs fork? Shouldn't it just point to the original repo which didn't had the clashing commit ?