fix(cmd): clarify empty gitea case control flow in supersedeOldReviews

The empty case "gitea": body exits the switch and continues to the
Gitea-specific logic below. Replace the vague comment with an explicit
note about the fall-through intent, per self-review feedback.

cmd/review-bot/main.go

@@ -535,7 +535,7 @@ func supersedeOldReviews(ctx context.Context, client vcs.Client, provider, vcsUR
 		}
 		return nil
 	case "gitea":
-		// Gitea: EditComment + ResolveComment flow
+		// Fall through to Gitea-specific logic below the switch.
 	default:
 		return fmt.Errorf("supersedeOldReviews: unsupported provider %q", provider)
 	}