Polish, 处理部分警告

HMCLCore/src/main/java/org/jackhuang/hmcl/auth/OfflineAccount.java

@@ -47,6 +47,7 @@ public class OfflineAccount extends Account {
             throw new IllegalArgumentException("Username cannot be blank");
     }
 
+    @Override
     public UUID getUUID() {
         return UUIDTypeAdapter.fromString(uuid);
     }