remove references to old Qt 'moc' timestamp files

src/moc.qt[56] existed briefly but got replaced by src/Qt[56].h-t
(controlled by hints/include/compiler.370).  The old names were
deliberately left in src/.gitignore and sys/unix/Makefile.src's
'clean' target to give some time for anyone who had generated them
to run 'make clean' to get rid of them.  That time is now up.  It's
only been about three weeks but if I wait any longer I'll probably
forget.

src/.gitignore

@@ -14,7 +14,6 @@ nethack
 *.o
 tiles.bmp
 *.moc
-moc.qt*
 *.lnk
 graphicschk
 nhdat

sys/unix/Makefile.src

@@ -746,7 +746,7 @@ tags: $(CSOURCES)
 	@( cd ../util ; $(MAKE) tags )
 
 clean:
-	-rm -f *.o $(HACK_H) $(CONFIG_H) moc.qt*
+	-rm -f *.o $(HACK_H) $(CONFIG_H)
 	-rm -f monstr.c vis_tab.c ../include/vis_tab.h #obsolete generated files
 	$(CLEANMORE)