Merging the default branch into a PR, from the API

When contributors raise PRs to Renovate , there are times where they'll merge main into their PR while they're waiting for a merge. Because we use a Merge Queue, we don't necessarily need this - as maintainers we'll manually merge main into a PR if we think it needs it, but it's mostly a case of waiting for the Merge Queue to handle it. Although we have a label that we add if we notice the author…