title: Remove(Delete) existing channel
body: <p>I built fabric network using kafka.<br/>
  Then, I created 2 channels such as "channel_A" and "channel_B".<br/></p>
  
  <p>Now, I don't need "channel_B".<br/>
  So, I want to remove(delete) this "channel_B" from my network.<br/></p>
  
  <p>Is there any way to remove(delete) it?<br/></p>