Update license headers to compact SPDX format.

License has not changed, this is just more compact and doesn't include years.
Bump version for RB.

src/main/java/net/minecraftforge/server/ServerLifecycleHooks.java

@@ -1,20 +1,6 @@
 /*
- * Minecraft Forge
- * Copyright (c) 2016-2021.
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation version 2.1
- * of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * Minecraft Forge - Forge Development LLC
+ * SPDX-License-Identifier: LGPL-2.1-only
  */
 
 package net.minecraftforge.server;