Stubsabot isn't updating open stubsabot PRs

[AlexWaygood]

If I understand correctly, stubsabot has logic that should mean that it auto-updates PRs (providing no manual changes have been made to the PR branch by maintainers).

That part of the script doesn't seem to be working correctly. #8490 was filed by stubsabot on August 5th, to bump types-stripe from 3.5.* to 4.0.*. But since then, stripe 4.1 was released on August 19th. Since no maintainers have pushed to that PR branch, I think stubsabot should have force-pushed to that branch so that the PR proposes updating to 4.1.* instead of 4.0.* -- but it hasn't.

https://github.com/python/typeshed/issues/8778#tasklist-block-e07bdbeb-93d3-4b63-bbcc-ba29a36d73bc