chore: move QC-fixture comment to the METPO prefix-normalization PR

The fixture explanatory comment belongs with the work that normalizes that
file's metpo: -> METPO: prefix (issue #16), so it is re-added there in the
canonical uppercase form. This PR keeps only the Makefile and OWL findings.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: turbomam

tests/sparql_qc/qc-positive-fixture.ttl

@@ -50,9 +50,6 @@ metpo:9999003 a owl:Class ;
     rdfs:label "fixture: a label that wrongly embeds http://example.org/foo" .
 
 # -> multiple-replaced_by-violation.sparql : two distinct IAO:0100001 (term replaced by) values
-# metpo:1000000 and metpo:2000000 are intentional fixture-only IRIs: they supply
-# two distinct replacement targets for this violation case and are not declared
-# here, nor expected to exist as production METPO terms.
 metpo:9999004 a owl:Class ;
     rdfs:label "fixture: two different replacements" ;
     IAO:0100001 metpo:1000000 , metpo:2000000 .