knot: remove redundant includes

src/knot/server/server.h

src/knot/updates/apply.c

src/knot/updates/zone-update.c

src/knot/zone/events/events.c

src/knot/zone/events/events.h

src/knot/zone/events/handlers.c

src/knot/zone/events/handlers.h

src/knot/zone/events/replan.c

src/knot/zone/events/replan.h

src/knot/zone/node.c

src/knot/zone/node.h

src/knot/zone/serial.c

src/knot/zone/timers.c

src/knot/zone/timers.h

src/knot/zone/zone-diff.h

src/knot/zone/zone-dump.h

src/knot/zone/zone-tree.c

src/knot/zone/zone-tree.h

src/knot/zone/zone.c

src/knot/zone/zone.h