Do a pull in case docs were updated during build
# What does this PR do?

Now that the build of the documentation takes a long time, it can happen that the doc has changed when trying to update the doc-build repo in the case of a release (for instance there was a failure with the v4.17.0 release doc update since the master doc was updated during its build).
This PR stashes, pulls and pops the stash to avoid that.
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_15922). All of your documentation changes will be reflected on that endpoint.