Make reuse compliant

src/main/resources/hotswap-agent.properties

@@ -1,20 +1,6 @@
+# SPDX-FileCopyrightText: 2023 Linnea Gr<47>f <nea@nea.moe>
 #
-# Firmament is a Hypixel Skyblock mod for modern Minecraft versions
-# Copyright (C) 2023 Linnea Gräf
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program 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 General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <https://www.gnu.org/licenses/>.
-#
+# SPDX-License-Identifier: CC0-1.0
 
 disabledPlugins=Log4j2,Proxy
 LOGGER=info