Fix description of the post_request hook signature

[PeterJCLaw]

trafficstars

I'm guessing that the previous description either pre-dates the current signature or was a copy/paste from pre_request. The new description was established from the signature example and inspection of the calling code.

[laggardkernel]

The post_request hook function could be defined with less arguments. worker, req are must, others are optional. Check test_config.test_post_request() and config.validate_post_request() for detail. Propose to improve the doc to make this clear.

@benoitc Any idea why the CI failed? This PR just changed the docs. Similar things happened in my PRs as well.

[PeterJCLaw]

Aha, thanks, I'd missed that. I've updated the suggested change.

[PeterJCLaw]

Hrm, rebasing on master doesn't seem to have fixed CI either.

@benoitc is there anything I can do to help here?