NS1: Remove tests for NS1_URLFWD

[tlimoncelli]

CC @costasd

Remove tests for NS1's URLFWD record. It is no longer supported.

=== FAIL: integrationTest TestDNSProviders/***integration.io/72:NS1_URLFWD_tests:Add_a_urlfwd (0.12s)
    integration_test.go:248: 
        + CREATE urlfwd1.***integration.io NS1_URLFWD / http://example.com/ 302 2 0 ttl=300
WARNING: NS1_URLFWD is deprecated and may stop working anytime now. Please avoid such records going forward.
    integration_test.go:253: PUT https://api.nsone.net/v1/zones/***integration.io/urlfwd1.***integration.io/URLFWD: 410 create record of URLFWD type is permanently disabled
        --- FAIL: TestDNSProviders/***integration.io/72:NS1_URLFWD_tests:Add_a_urlfwd (0.12s)