Add forget Action for removed block

[ilya-hontarau]

Removed block introduced a new action, "forget", that is missing now
https://developer.hashicorp.com/terraform/language/resources/syntax#removing-resources

How to reproduce:
Apply pet1, then change to

# resource "random_pet" "pet1" {
#   length = 5
# }

removed {
  from = random_pet.pet1

  lifecycle {
    destroy = false
  }
}

terraform plan -out tf.plan
terraform show -json tf.plan