Add #851 to History

After discussing with Evan, my concerns in eaf89a have been adequately
addressed.

Fixes #851

History.txt

@@ -40,6 +40,8 @@ Bug fixes:
   now.  Bug #821 by johnny5-.
 * Gem dependency API supports lockfiles without explicit sources.  Bug #820 by
   johnny5-.
+* Gem dependency API supports lockfiles with multiple sources.  Bug #822 by
+  johnny5-, bug #851 by sumit shah.
 * Gem dependency API supports lockfiles with git sources using branch, tag and
   ref.  Bug #822 by johnny5-.
 * SSL configuration entries in ~/.gemrc are properly round-tripped.  Bug #837