Revert "gdbus-codegen: emit GUnixFDLists if an arg has type 'h'"
This reverts commit 4aba0356, preserving the new tests but adjusting them to assert that the old behaviour is restored.
As expected, there were a few projects which broke because of this. Unfortunately, in one case the breakage crosses a project boundary: sysprof ships D-Bus introspection XML, which is consumed by mutter and passed through gdbus-codegen.
Since sysprof cannot add this annotation without breaking its existing users, a warning is also not appropriate.