pg_dump: Remove unnecessary code for security labels on extensions.

Commit d9572c4e3b added extension support and made pg_dump attempt to
dump security labels on extensions. However, security labels on extensions
are not actually supported, so this code was unnecessary.

This commit removes it.

Suggested-by: Jian He <jian.universality@gmail.com>
Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxF8=z0v=888NKKEoTHQ+Jc4EXutFi91BF0fFjgFsZT6JQ@mail.gmail.com

src/bin/pg_dump/pg_dump.c

@@ -12023,17 +12023,12 @@ dumpExtension(Archive *fout, const ExtensionInfo *extinfo)
 								  .createStmt = q->data,
 								  .dropStmt = delq->data));
 
-	/* Dump Extension Comments and Security Labels */
+	/* Dump Extension Comments */
 	if (extinfo->dobj.dump & DUMP_COMPONENT_COMMENT)
 		dumpComment(fout, "EXTENSION", qextname,
 					NULL, "",
 					extinfo->dobj.catId, 0, extinfo->dobj.dumpId);
 
-	if (extinfo->dobj.dump & DUMP_COMPONENT_SECLABEL)
-		dumpSecLabel(fout, "EXTENSION", qextname,
-					 NULL, "",
-					 extinfo->dobj.catId, 0, extinfo->dobj.dumpId);
-
 	free(qextname);
 
 	destroyPQExpBuffer(q);