doctor: Don't say All done when no checks were run

When there were no checks run, don't say "All done", but "No checks to
run" instead, to make it clear what happened.

Addresses another part of #1905.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

modules/doctor/doctor.go

@@ -104,7 +104,11 @@ func RunChecks(ctx context.Context, colorize, autofix bool, checks []*Check) err
 			logger.Info("OK")
 		}
 	}
+	if len(checks) > 0 {
 		logger.Info("\nAll done.")
+	} else {
+		logger.Info("\nNo checks to run.")
+	}
 	return nil
 }