Remove an extra "`" from the documentation

Summary: One too many.

Test Plan: Counted carefully.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17137

src/docs/contributor/version.diviner

@@ -65,7 +65,7 @@ In most cases, you can find the upstream commit you've branched from like this:
 
 ```
 $ git merge-base HEAD origin/master
-````
+```
 
 Note that if you report a bug and have local commits, we will almost always ask
 you to reproduce the issue against a clean copy of Phabricator before we