docs(example): remove manage_own_password_without_mfa

Since [make deny optional. allow users to change passwords without
mfa](0e7b829)
has been commit, the manage_own_password_without_mfa variable in
[example](https://github.com/terraform-module/terraform-aws-enforce-mfa/blob/master/examples/basic/main.tf)
file doesn't have up-to-date.

#33

Author: Yosapol Jitrak

examples/basic/main.tf

@@ -11,7 +11,6 @@ module "enforce_mfa" {
   policy_name                     = "managed-mfa-enforce"
   account_id                      = data.aws_caller_identity.current.id
   groups                          = [aws_iam_group.support.name]
-  manage_own_password_without_mfa = true
   manage_own_signing_certificates = true
   manage_own_ssh_public_keys      = true
   manage_own_git_credentials      = true