Backport #32999 by @a1012112796
user with read permission should also can create agit flow pull request.
looks this logic was broken in
https://github.com/go-gitea/gitea/pull/31033 this pull request try fix
it and add test code.
Signed-off-by: a1012112796 <1012112796@qq.com>
Co-authored-by: a1012112796 <1012112796@qq.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>