doc: fix layout problem in v4 changelog

The current layout is breaking the release post tool.

This commit also removed erroneous entires in the main CHANGELOG for
v4.4.6 and v5.12.0.

PR-URL: https://github.com/nodejs/node/pull/7394
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

CHANGELOG.md

@@ -159,14 +159,6 @@ release.
 ----
 ----
 
-## 2016-06-23, Version 5.12.0 (Stable), @evanlucas
-
-<a href="doc/changelogs/CHANGELOG_V5.md#5.12.0">Moved to doc/changelogs/CHANGELOG_V5.md#5.12.0</a>.
-
-## 2016-06-23, Version 4.4.6 'Argon' (LTS), @thealphanerd
-
-<a href="doc/changelogs/CHANGELOG_V4.md#4.4.6">Moved to doc/changelogs/CHANGELOG_V4.md#4.4.6</a>.
-
 ## 2016-05-06, Version 0.12.14 (Maintenance), @rvagg
 
 <a href="doc/changelogs/CHANGELOG_V012.md#0.12.14">Moved to doc/changelogs/CHANGELOG_V012.md#0.12.14</a>.

doc/changelogs/CHANGELOG_V4.md

@@ -48,9 +48,10 @@
 will be supported actively until April 2017 and maintained until April 2018.
 
 <a id="4.4.6"></a>
-
 ## 2016-06-23, Version 4.4.6 'Argon' (LTS), @thealphanerd
 
+### Notable Changes
+
 This is an important security release. All Node.js users should consult the security release summary at nodejs.org for details on patched vulnerabilities.
 
 This release is specifically related to a Buffer overflow vulnerability discovered in v8, more details can be found [in the CVE](https://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1669)