Update CHANGELOG.md for 10.4.7

[ci skip]

CHANGELOG.md

@@ -501,6 +501,14 @@ entry.
 - Adds empty state illustration for pending job.
+## 10.4.7 (2018-04-03)
+
+### Security (2 changes)
+
+- Fix XSS on diff view stored on filenames.
+- Adds confidential notes channel for Slack/Mattermost.
+
+
 ## 10.4.6 (2018-03-16)
 ### Security (2 changes)