doc: remove spurious new line in CHANGELOG_V6.md

PR-URL: https://github.com/nodejs/node/pull/8009
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/changelogs/CHANGELOG_V6.md

@@ -30,7 +30,6 @@
 October 2016.
 
 <a id="6.3.1"></a>
-
 ## 2016-07-21, Version 6.3.1 (Current), @evanlucas
 
 ### Notable changes