Bugfix: honor upstream default for enableEndpointIndependentMapping

As discussed previously in hashicorp/terraform-provider-google#10547
and GoogleCloudPlatform#5942, the default value for enableEndpointIndependentMapping has
been changed in the API to be `false`.

This commit changes the handling of the flag to point at the upstream
default.

mmv1/products/compute/api.yaml

@@ -13533,10 +13533,8 @@ objects:
       - !ruby/object:Api::Type::Boolean
         name: enableEndpointIndependentMapping
         description: |
-          Specifies if endpoint independent mapping is enabled. This is enabled by default. For more information
+          Specifies if endpoint independent mapping is enabled. This is disabled by default. For more information
           see the [official documentation](https://cloud.google.com/nat/docs/overview#specs-rfcs).
-        default_value: true
-        send_empty_value: true
   - !ruby/object:Api::Resource
     name: 'RouterBgpPeer'
     base_url: projects/{{project}}/regions/{{region}}/routers/{{router}}

mmv1/products/compute/terraform.yaml

@@ -2512,6 +2512,8 @@ overrides: !ruby/object:Overrides::ResourceOverrides
         custom_flatten: 'templates/terraform/custom_flatten/default_if_empty.erb'
       enableDynamicPortAllocation: !ruby/object:Overrides::Terraform::PropertyOverride
         default_from_api: true
+      enableEndpointIndependentMapping: !ruby/object:Overrides::Terraform::PropertyOverride
+        default_from_api: true
     custom_code: !ruby/object:Provider::Terraform::CustomCode
       constants: 'templates/terraform/constants/router_nat.go.erb'
       resource_definition: 'templates/terraform/resource_definition/router_nat.go.erb'