Control concurrency of PR deployment jobs

[karl-johan-grahn]

Currently, multiple PR jobs triggered at the same time can cause this error in the "Deploy PR docs" step:

error: failed to push branch pull-request-deployments to origin:
  To https://github.com/stakater/mto-docs
   ! [rejected]          pull-request-deployments -> pull-request-deployments (fetch first)
  error: failed to push some refs to 'https://github.com/stakater/mto-docs'
  hint: Updates were rejected because the remote contains work that you do not
  hint: have locally. This is usually caused by another repository pushing to
  hint: the same ref. If you want to integrate the remote changes, use
  hint: 'git pull' before pushing again.
  hint: See the 'Note about fast-forwards' in 'git push --help' for details.
Error: Process completed with exit code 1.

This often happens when Renovate opens dependency updates for multiple doc branches at the same time. This is mainly a problem for versioned docs, since it contains multiple branches with similar dependencies.

What this change should do is group all deployment jobs into a group called pull_request_versioned_doc and only execute jobs in that group sequentially. Any jobs in progress will not be canceled. Read more about concurrency here.

[github-actions]

@stakater-user Image is available for testing. docker pull ghcr.io/stakater/mto-docs:v0.0.207

[github-actions]

@karl-johan-grahn Image is available for testing. docker pull ghcr.io/stakater/mto-docs:SNAPSHOT-PR-265-04337dd0

[github-actions]

@karl-johan-grahn PR doc deploy was successfully deleted from branch pull-request-deployments