Generating previews flow seems to take longer than expected

[alan707]

The development flow for changes is too slow if we are expecting people to use bazelbuild/bazel

[armandomontanez]

An example where this happened is bazelbuild/bazel#29328:

PR	Time created
Original PR	April 17, 3:07pm PDT
bazel-docs Preview	April 20, 8:59am PDT

However, my most recent PR got a preview in only ~14 min which is totally acceptable. I'm not sure if this is an issue on GitHub's side, or something we have control over.