fix(useragent): unsafe, but working implementation of ml-dsa

useragent/lib/features/identity/pk_manager.dart

@@ -1,11 +1,6 @@
-enum KeyAlgorithm {
-  rsa, ecdsa, ed25519
-}
-
-// The API to handle without storing the private key in memory. 
+// The API to handle without storing the private key in memory.
 //The implementation will use platform-specific secure storage and signing capabilities.
 abstract class KeyHandle {
-  KeyAlgorithm get alg;
   Future<List<int>> sign(List<int> data);
   Future<List<int>> getPublicKey();
 }