Fix build under OPTIMIZER_DEBUG.

In commit 19a54114 I replaced RelOptInfo.width with
RelOptInfo.reltarget.width, but I missed updating debug_print_rel()
for that because it's not compiled by default.
Reported by Salvador Fandino, patch by Michael Paquier.

src/backend/optimizer/path/allpaths.c

@@ -2957,7 +2957,7 @@ debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
 
 	printf("RELOPTINFO (");
 	print_relids(rel->relids);
-	printf("): rows=%.0f width=%d\n", rel->rows, rel->width);
+	printf("): rows=%.0f width=%d\n", rel->rows, rel->reltarget.width);
 
 	if (rel->baserestrictinfo)
 	{