Fix implementation and tests

Author: leandrodamascena

aws_lambda_powertools/utilities/parser/models/__init__.py

@@ -157,7 +157,6 @@
     "CognitoPostConfirmationTriggerModel",
     "CognitoPreAuthenticationTriggerModel",
     "CognitoPostAuthenticationTriggerModel",
-    "CognitoPreTokenGenerationTriggerModel",
     "CognitoMigrateUserTriggerModel",
     "CognitoCustomMessageTriggerModel",
     "CognitoCustomEmailSenderTriggerModel",