More race conditions in GHA

[penelopeysm]

When merging a PR, there's a potential race condition between the publish workflow on main + the remove PR preview workflow.

Here the changes to main were being deployed but got interrupted when the remove PR preview workflow pushed to gh-pages. see https://github.com/TuringLang/docs/commits/gh-pages?since=2024-11-18&until=2024-11-19

[penelopeysm]

I don't really get the sense that this will cause any issues in practice. However, it seems like the sort of very subtle thing that could cause silent failures...