title: Coq : replace hypothesis into implication
body: <p>I am learning Coq and I encountered an issue : how can I switch from that context</p>
  <pre><code>HA : A
  HABC : A -&gt; B -&gt; C
  </code></pre>
  <p>to this one ?</p>
  <pre><code>HA : B -&gt; C
  </code></pre>
  <p>I tried apply and rewrite tactics but it did not work.</p>
  <p>Thank you for your help !</p>