title: How to remove index in rails
body: <p>I have found that I have two "survey_id" columns in my schema and that's been causing some problems for me. Specifically I need to remove the second index as I don't want survey_id to be unique.</p>
  
  <pre><code> add_index "completions", ["survey_id"], name: "index_completions_on_survey_id"
   add_index "completions", ["survey_id"], name: "index_completions_on_survey_id_and_user_id", unique: true
  </code></pre>
  
  <p>I've tried </p>
  
  <pre><code>def change
     remove_index "completions", ["survey_id"], name =&gt; "index_completions_on_survey_id_and_user_id"
   end
  </code></pre>
  
  <p>and</p>
  
  <pre><code>def change
     remove_index "completions", ["survey_id"], name: "index_completions_on_survey_id_and_user_id"
   end
  </code></pre>
  
  <p>But neither of those seem to work. What's the correct syntax for this migration to remove the index? I feel like this is basic and I'm just missing something stupid. Thanks in advance!</p>