update licenses

Author: Jonathing

src/main/groovy/net/minecraftforge/gradleutils/GradleUtilsFlowAction.java

@@ -1,3 +1,7 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
 package net.minecraftforge.gradleutils;
 
 import net.minecraftforge.gradleutils.shared.EnhancedFlowAction;