[9.20] fix: usr: Fix bug where zone switches from NSEC3 to NSEC after retransfer

When a zone is re-transferred, but the zone journal on an inline-signing secondary is out of sync, the zone could fall back to using NSEC records instead of NSEC3. This has been fixed.

Closes #5527

Backport of MR !11226

Merge branch 'backport-5527-retransfer-nsec3-bug-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11274