Fix issue with YAML aliases in ruby 3.1

[tigris]

I was testing out the docker implementation and noticed it recently bumped from 1.2.1 to 1.2.2. The listed changes for this release seemed non-breaking.

However, since the Dockerfile is not pinning to a specific version of ruby:alpine, it meant that ruby got upgraded to 3.1, which has a pretty nasty breaking yaml change.

This should help to resolve some of that, for my use case anyway.