Mapping set metadata score shouldn't be penalized for propagated metadata

[cthoyt]

There already appears to be a mechanism for subject source and object source that are annotated in the mappings instead of the mapping set get recognized

mapping-commons.github.io/scripts/cli.py

Lines 94 to 104 in 2d3003c

	def _inject_per_mapping_source(meta: dict, columns: list[str]) -> None:
	"""Mark subject_/object_source as present when only the TSV column exists.
	The prefix-implied case (no set-level value, no column, source derivable
	from subject_id/object_id CURIE prefixes) is intentionally not handled —
	see docs/per_mapping_source.md.
	"""
	col_set = set(columns)
	for field in ("subject_source", "object_source"):
	if field in col_set and not meta.get(field):
	meta[field] = PER_MAPPING_SOURCE

this should get extended to all other propagatable metadata