fix: remove duplicate IANA registry entry causing false update reports

docs/detailed-guide.md

@@ -529,9 +529,9 @@ poetry run pytest tests/ -v
 - `tests/test_cli.py`: 3 CLI parsing tests
 - `tests/test_iana_validator.py`: 20 IANA validation tests
 - `tests/test_iana_parse.py`: 14 IANA parsing tests
-- `tests/test_iana_update.py`: 13 IANA update tests
+- `tests/test_iana_update.py`: 14 IANA update tests
 
-**Total:** 63 tests
+**Total:** 64 tests
 
 **Test database setup:**