Agit returned result should be from `ProcReceive` hook but not
`PostReceive` hook. Then for all non-agit pull requests, it will not
check the pull requests for every pushing `refs/pull/%d/head`.
Backport #30104
(cherry picked from commit 6e3aaa997549b83935241e486caf811793c88aea)
Conflicts:
it is implemented differently in Forgejo, just keep the test
in tests/integration/git_push_test.go
