ElasticLoadBalancingV2TargetGroup required properties

[sinnott74]

Describe the bug
ElasticLoadBalancingV2-TargetGroup has required properties of Port, Protocol & VpcId. These are no longer required due to ALB + Lambda.

See If the target is a Lambda function, this parameter does not apply. in https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticloadbalancingv2-targetgroup.html#cfn-elasticloadbalancingv2-targetgroup-port

To Reproduce
Steps to reproduce the behavior:

1. Deploy an AWS::ElasticLoadBalancingV2::TargetGroup resource with a TargetType of lambda
2. Error:

ValidationError: [/Resources/LoadBalancerDeleteTargetGroup/Type/Port] 'null' values are not allowed in templates

Expected behavior
A AWS::ElasticLoadBalancingV2::TargetGroup can be deployed with a Port, Protocol or VpcId specified