fix(automation): node prs for >=16.x should point at `staging` branches

[darcyclarke]

Summary

Currently we're pointing the Node.js Dep Update PRs we created against the master branch which may not have the latest or staged changes as a maintainer is queuing up a release (ex. nodejs/node#39813).

Change

• Update references to master to be the relevant staging branch for the npm release (ref. https://github.com/npm/cli/blob/latest/.github/workflows/create-cli-deps-pr.yml#L30)

Reference:

• deps: upgrade npm to 7.21.0 nodejs/node#39813 (comment)

[wraithgar]

we only have a latest branch now and the node PRs point to the correct commits/changelogs