fix unused-param warning

libwccl/ops/match/conditions/isannotatedas.cpp

@@ -43,7 +43,7 @@ MatchResult IsAnnotatedAs::apply(const ActionExecContext& context) const
 	return MatchResult(ann_match);
 }
 
-std::string IsAnnotatedAs::to_string(const Corpus2::Tagset& tagset) const
+std::string IsAnnotatedAs::to_string(const Corpus2::Tagset& /*tagset*/) const
 {
 	std::ostringstream os;
 	os << name() << "(\"" << chan_name_ << "\")";