pDNS documention correction for CR forwarding rule. (IBM-Cloud#4695)

* Enabled argument updated in docs for PDNS glb resource

* reverting the change made to main branch wrongly

* Document correction for CR forwarding rule type

* Corrected documentation for forwarding rule type value

website/docs/r/dns_custom_resolver_forwarding_rule.html.markdown

@@ -74,7 +74,7 @@ Review the argument reference that you can specify for your resource.
 * `resolver_id` - (Required, String) The unique identifier of a custom resolver.
 * `description` - (Optional, String) Descriptive text of the forwarding rule.
 * `type` - (Optional, String) Type of the forwarding rule.
-  * Constraints: Allowable values are: `zone`, `hostname`,`Default`.
+  * Constraints: Allowable values is: zone.
 * `match` - (Optional, String) The matching zone or hostname.
 * `forward_to` - (Optional, List) The upstream DNS servers will be forwarded to.