Authenticate audiences-ruby.yml workflow against internal registry

[c-gerke]

Similar to the change in powerhome/github-actions-workflows#40, this PR adds a step to authenticate against our internal NPM registry so it can pull the NPM packages that Renovate rewrites.

This can be seen completing successfully when this same change is applied to a branch in this workflow.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 24 hours if no further activity occurs.
If this change is desirable, please accelerate completing it. If it is not, please close the PR. If you're blocked on something, please ensure there's a reference to this PR in a story on your team's board so the team will follow up, and consider closing the PR for now.
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Thank you for your contributions and your collaboration in reducing WIP and cycle time.