Update pulumi-hugo PR workflow to lint PRs from forks

[toriancrane]

Whenever someone creates a PR against pulumi-hugo from a fork, linting does not run against that PR. It would be great if we could enable the linting checks for PRs coming from forks.

[jkodroff]

Given that linting runs as a pre-commit hook and that PRs coming from forks are relatively rare, I don't see us doing this anytime soon. Closing as won't fix.