Add rspec-otel to registry

[dmathieu]

This adds the rspec-otel gem to the registry.
https://rubygems.org/gems/rspec-otel

[dmathieu]

I suppose the repo URL needs to be added to refcache.
But I don't see any documentation about doing so in the repository, and my attempt to add it manually don't resolve the failure.

[svrnm]

/fix:refcache

[github-actions]

You triggered fix:refcache action run at https://github.com/open-telemetry/opentelemetry.io/actions/runs/7898578321

[svrnm]

I suppose the repo URL needs to be added to refcache. But I don't see any documentation about doing so in the repository, and my attempt to add it manually don't resolve the failure.

yes, we need to document this better in our contributor guidelines