chore: update LICENSE

Author: quiteboring

src/main/resources/fabric.mod.json

@@ -13,7 +13,7 @@
     "homepage": "https://cobalt.quiteboring.dev/",
     "sources": "https://github.com/CobaltScripts/Cobalt"
   },
-  "license": "CC0-1.0",
+  "license": "GPL-3.0",
   "icon": "assets/cobalt/icon.png",
   "environment": "*",
   "entrypoints": {