using -1 as the column is not used on the user facing function

Author: cvvergara

src/components/articulationPoints.c

@@ -91,7 +91,7 @@ PGDLLEXPORT Datum _pgr_articulationpoints(PG_FUNCTION_ARGS) {
             nulls[i] = false;
         }
 
-        values[0] = Int64GetDatum((int64_t)funcctx->call_cntr + 1);
+        values[0] = Int32GetDatum(-1);
         values[1] = Int64GetDatum(result_tuples[funcctx->call_cntr]);
 
         tuple = heap_form_tuple(tuple_desc, values, nulls);