Remove obsolete TODO.

Per the analysis in https://crbug.com/725689, the equivalent functionality
of ShouldServiceRequest is present with PlzNavigate, which means this
comment is now obsolete.

BUG=725689

Review-Url: https://codereview.chromium.org/2910793002
Cr-Commit-Position: refs/heads/master@{#475791}

content/browser/loader/resource_dispatcher_host_impl.cc

@@ -2022,9 +2022,6 @@ void ResourceDispatcherHostImpl::BeginNavigationRequest(
       !is_external_protocol;
 
   if (is_shutdown_ || non_web_url_in_guest ||
-      // TODO(davidben): Check ShouldServiceRequest here. This is important; it
-      // needs to be checked relative to the child that /requested/ the
-      // navigation. It's where file upload checks, etc., come in.
       (delegate_ && !delegate_->ShouldBeginRequest(
           info.common_params.method,
           info.common_params.url,