update IRC URLs to https

Author: pchampin

index.html

@@ -381,8 +381,8 @@ <h2>Contributing</h2>
       <li>Technical discussion typically occurs on the public mailing list:
         <a href="https://lists.w3.org/Archives/Public/public-json-ld-wg/">[email protected]</a></li>
 
-      <li>The working group uses <a href="http://irc.w3.org/?channels=json-ld">#json-ld</a>
-        IRC channel is available for real-time discussion on <a href="http://irc.w3.org">irc.w3.org</a>.</li>
+      <li>The working group uses <a href="https://irc.w3.org/?channels=json-ld">#json-ld</a>
+        IRC channel is available for real-time discussion on <a href="https://irc.w3.org">irc.w3.org</a>.</li>
 
       <li>The <a href="https://webchat.freenode.net/?channels=json-ld">#json-ld</a>
         IRC channel is also available for real-time discussion on irc.freenode.net.</li>