Keep the comparator from last_known_affected_version_range

[arpitjain099]

get_last_known_affected_version parses GitHub's last_known_affected_version_range into a range and then returns only affected_version_range.constraints[0].version, dropping the comparator. get_version_ranges_constraints puts it back as <=:

affected_constraint = VersionConstraint(comparator="<", version=v_obj)
if db_specific_explicit_last_known:
    affected_constraint = VersionConstraint(
        comparator="<=", version=db_specific_explicit_last_known
    )

The value is usually <=, so most of the time this is a no-op. When GitHub publishes a strict <, the rewrite marks one more version affected than GitHub says. GHSA-x684-96hh-833x is an example: the API gives >= 5.0.0-RC1, < 5.5.5 and this produces vers:composer/>=5.0.0-RC1|<=5.5.5, so Craft CMS 5.5.5, a real release that is not affected, is reported as affected.

The second entry in that same advisory comes out right, because it has no last_known_affected_version_range and takes the plain < path.

Now the helper returns the whole VersionConstraint and the caller uses it as parsed. I counted the GHSA corpus while looking at this: of 1916 affected entries carrying a last_known_affected_version_range, 1755 are <= and unaffected by this, 161 are a strict <, and 106 of those are in an ecosystem github_osv_importer_v2 imports.

Two cases added to test_osv_v2.py: the helper keeps < and <= as published, and get_version_ranges_constraints carries a strict bound through. Both fail on main, 20 pass here, black and isort clean.