Does not update cached scipy-proceedings builder if upstream scipy-proceedings changes

[mpacer]

Not sure why this doesn't work. I had thought it did but after the info changed, in a recent PR (scipy-conference/scipy_proceedings#303) it still has the old info.

Probably need to check the hook checking code & make sure it is triggered on merged PRs.

[mpacer]

Possible additional information: update_prs does not update cached scipy-proceedings/. If you delete scipy-proceedings/ it will not be pulled down until a paper is built. That may be what triggers it (we may want to either add the code that does this to update_prs or runserver.