Remove net-firewall-policy match variable validation

[richard-olson]

The current Terraform validation for the match variable in the net-firewall-policy module prevents the use of new match options such as FQDNs and Threat Intelligence unless they are combined with destination/source range for egress and ingress rules respectively.

Per #1615 the preferred approach would be to remove the validation check.

[juliocc]

I think you'll have to run tfdoc.py to update the readme.