Revert "commit-graph: when incompatible with graphs, indicate why"

This reverts commit c85eec7, as
it is a bit overzealous, we are in prerelease freeze, and we want
to have enough time to get this right and cook in 'next'.

cf. <[email protected]>

Author: gitster

commit-graph.c

@@ -205,24 +205,16 @@ static int commit_graph_compatible(struct repository *r)
 
 	if (read_replace_refs) {
 		prepare_replace_object(r);
-		if (hashmap_get_size(&r->objects->replace_map->map)) {
-			warning(_("repository contains replace objects; "
-			       "skipping commit-graph"));
+		if (hashmap_get_size(&r->objects->replace_map->map))
 			return 0;
-		}
 	}
 
 	prepare_commit_graft(r);
 	if (r->parsed_objects &&
-	    (r->parsed_objects->grafts_nr || r->parsed_objects->substituted_parent)) {
-		warning(_("repository contains (deprecated) grafts; "
-		       "skipping commit-graph"));
+	    (r->parsed_objects->grafts_nr || r->parsed_objects->substituted_parent))
 		return 0;
-	}
-	if (is_repository_shallow(r)) {
-		warning(_("repository is shallow; skipping commit-graph"));
+	if (is_repository_shallow(r))
 		return 0;
-	}
 
 	return 1;
 }