title: MongoDB golang driver not returns unrecognized field `hint` when using hint with CountDocument
body: <p>So I am using the official mongo driver for go <code>go.mongodb.org/mongo-driver</code> and I am running mongodb v4 in a container. All operations work fine but when I try to add a hint to CountDocument it fails with an error saying <code>unrecognized field hint</code>. I have seen this error reported in old gh issues and jira threads but the problem in those cases was that people were using mongo versions older than 3.6 but I am using v4 so I can't figure out the problem.</p>
  
  <pre><code>opts := &amp;options.CountOptions{}
  opts.SetHint("client_1_created_at_1")
  
  count, err := r.collection.CountDocuments(ctx, query, opts)
  if err != nil {
      return 0, err
  }
  return count, nil
  </code></pre>
  
  <p>MongoDB version: 4.0.6
  Mongo Driver version: 1.0.1</p>