title: How to undo setting Elasticsearch Index to readonly?
body: <p>So I just set one of my indices to readonly, and now want to delete it.</p>
  
  <p>To set it to readonly:</p>
  
  <pre><code>PUT my_index/_settings
  { "index": { "index.blocks.read_only" : true } }
  </code></pre>
  
  <p>When I tried to delete it I got this response:</p>
  
  <pre><code>ClusterBlockException[blocked by: [FORBIDDEN/5/index read-only (api)];]
  </code></pre>
  
  <p>Then I tried to set the index to readonly false:</p>
  
  <pre><code>PUT my_index/_settings
  { "index": { "index.blocks.read_only" : false } }
  </code></pre>
  
  <p>But that gives the same error message as above. So how to set readonly back to false?</p>