Ignore 'prn' field on metadata comparing tests

The prn field is not RPM metadata, it is pulp specific metadata,
so this can be safely ignored.

Prn was introduced in pulp/pulpcore#5813

pulp_rpm/tests/functional/api/test_sync.py

@@ -944,7 +944,7 @@ def test_core_metadata(init_and_sync, rpm_package_api):
     diff = dictdiffer.diff(
         package,
         RPM_COMPLEX_PACKAGE_DATA,
-        ignore={"time_file", "pulp_created", "pulp_last_updated", "pulp_href"},
+        ignore={"time_file", "pulp_created", "pulp_last_updated", "pulp_href", "prn"},
     )
     assert list(diff) == [], list(diff)