[docs] remove extra slash from llvm github url

Reviewed By: tstellar

Differential Revision: https://reviews.llvm.org/D137418

Author: sloorush

llvm/docs/_templates/indexsidebar.html

@@ -25,5 +25,5 @@ <h3>Additional Links</h3>
     <li><a href="https://llvm.org/docs/FAQ.html">FAQ</a></li>
     <li><a href="https://llvm.org/docs/Lexicon.html">Glossary</a></li>
     <li><a href="https://llvm.org/pubs">Publications</a></li>
-    <li><a href="https://github.com/llvm/llvm-project//">Github Repository</a></li>
+    <li><a href="https://github.com/llvm/llvm-project/">Github Repository</a></li>
 </ul>