Fix license in fabric.mod.json

src/main/resources/fabric.mod.json

@@ -12,7 +12,7 @@
     "sources": "https://gitlab.com/Lortseam/better-mount-hud",
     "issues": "https://gitlab.com/Lortseam/better-mount-hud/-/issues"
   },
-  "license": "Apache-2.0",
+  "license": "GPL-3.0",
   "environment": "client",
   "mixins": [
     {