Update license headers

src/knot/dnssec/nsec-chain.c

src/knot/dnssec/nsec-chain.h

src/knot/dnssec/nsec3-chain.c

src/knot/dnssec/zone-nsec.c

src/knot/events/handlers/expire.c

src/knot/journal/serialization.h

src/knot/nameserver/axfr.c

src/knot/nameserver/internet.c

src/knot/updates/zone-update.h

src/knot/zone/zone-diff.c

src/knot/zone/zone-tree.h

tests/knot/test_changeset.c

tests/knot/test_zone-tree.c