In commit 7fa7f55230, the Autogen/SameName test
was changed to not test .hh header file processing in AUTOGEN anymore,
because we had to revert that feature. Since we now support .hh header file
processing in AUTOMOC again, we can restore the Autogen/SameName test for
that.
Since commit 4a9154537c (Autogen: Use cmake::IsHeader/SourceExtension
for file type detection, 2019-07-02, v3.16.0-rc1~470^2~4) we process
`.hh` files with `AUTOMOC`. However, this change can break existing
projects that do not expect the behavior. Revert it for now. It can
be restored later via a policy.
Fixes: #20101
