dirmngr: More w32 system daemon cleanup

* dirmngr/dirmngr.c (handle_tick): Remove w32 tests for
shutdown_pending; no longer needed.

In d83ba4897bf217d1045c58d1b99e52bd31c58812, we removed the
Windows-specific system daemon features, where shutdown_pending was
set from w32_service_control(). shutdown_pending is now never
assigned outside of handle_signal() or within an inotify test, neither
of which are available on w32.

As a result, this stanza in handle_tick() should be dead code, and can
be removed to keep things simple.

s/win32/w32/ to please RMS ;-) -wk

• Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>