fix: make mixin json more correct

Author: uku3lig

src/main/resources/smoothboot.mixins.json

@@ -1,8 +1,8 @@
 {
   "required": true,
-  "minVerscomn": "0.8",
+  "minVersion": "0.8",
   "package": "com.github.getchoo.smoothboot.mixin",
-  "compatibilityLevel": "JAVA_8",
+  "compatibilityLevel": "JAVA_21",
   "mixins": ["UtilMixin"],
   "client": ["client.MainMixin", "client.IntegratedServerMixin"],
   "server": ["server.MainMixin"],