qemu-tech: Fix dangling @menu entries

Recent commit 2f2c4e47 "Convert "translator internals" docs to RST,
move to devel manual" and commit 282d36b5 "qemu-tech.texi: Remove
"QEMU compared to other emulators" section" removed @node, but left
their @menu entries behind.  This broke building qemu-doc.info (but
not qemu-doc.{html,pdf,txt}; how odd).  Bury the dead @menu entries.

Reported-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Fixes: 2f2c4e47
Fixes: 282d36b5
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190715055736.15214-3-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>