Fixed type of CognitoEvent version attribute. int => String

[chirag729]

version attribute for CognitoEvent comes through as a String.

{
    "version": "1",
    "region": "us-east-1",
    "userPoolId": "us-east-1_eQ3CWqhez",
    "userName": "2b37ddf6-277e-4c4d-b9d7-2e366a85489c",
    "callerContext": {
        "awsSdkVersion": "aws-sdk-unknown-unknown",
        "clientId": "3p3baj8uej3qos8k1ekfg6a4ed"
    },
    "triggerSource": "PostConfirmation_ConfirmSignUp",
    "request": {
        "userAttributes": {
            "sub": "2b37ddf6-277e-4c4d-b9d7-2e366a85489c",
            "birthdate": "1994-06-16",
            "email_verified": "true",
            "cognito:user_status": "CONFIRMED",
            "cognito:email_alias": "*******@******",
            "email": "*******@******"
        }
    },
    "response": {}
}