[libbeat] Update error message for regenerating files during build (e…

…lastic#22277)

dev-tools/mage/check.go

@@ -61,7 +61,7 @@ func Check() error {
 		}
 
 		return errors.Errorf("some files are not up-to-date. "+
-			"Run 'mage fmt update' then review and commit the changes. "+
+			"Run 'make update' then review and commit the changes. "+
 			"Modified: %v", changes)
 	}
 	return nil