test(network): enable case for GetBgpServiceCommunities (Azure#26252)

Previously it's blocked by the return value contains malformed value for `id` property, like `/subscriptions//resourceGroups//...` which will cause parsing error in `ResourceIdentifier`.
But now since all `Network` resources will inherit its own `Resource` type of which `id` property is just a string. The parsing problem doesn't exist anymore. We can simply just enable the test.

resolve Azure/autorest.csharp#1828

Author: archerzz