title: Topic limit exceeded error thrown when updating PushTopic
body: <p>I can create and update <code>PushTopics</code> without issue until the limit is reached. Once the limit is reached, I can't update existing topics, the following error is thrown:</p>
  
  <blockquote>
    <p>Update failed. First exception on row 0 with id xxx; first error:
    LIMIT_EXCEEDED, exceeded the maximum allowed number of push topics: []</p>
  </blockquote>
  
  <pre><code>[note - xxx == Id of the PushTopic]
  </code></pre>
  
  <p>I am not inserting or upserting - just updating the query. </p>
  
  <p>If the org limit is 20 topics, everything works perfectly up until 19 topics. At 20 topics this error is thrown. </p>
  
  <p>Is there a workaround for this?</p>