Add v3.5.0-beta.4 to CHANGELOG

[ci skip]

(cherry picked from commit 942fdb7)

CHANGELOG.md

@@ -1,8 +1,8 @@
 # Ember Changelog
 
-### v3.6.0-beta.1 (Unreleased)
+### v3.5.0-beta.4 (October 1, 2018)
 
-- [#17003](https://github.com/emberjs/ember.js/pull/17003) / [#17013](https://github.com/emberjs/ember.js/pull/17013) [BUGFIX] Fix rendering of empty content with `{{{...}}}` and `htmlSafe`
+- [#17003](https://github.com/emberjs/ember.js/pull/17003) / [#17013](https://github.com/emberjs/ember.js/pull/17013) [BUGFIX] Fix rendering of empty content with `{{{...}}}` or `{{...}}` with `htmlSafe('')`
 
 ### v3.5.0-beta.3 (September 24, 2018)