updated CHANGELOG for 3.3.8

Author: fabpot

CHANGELOG-3.3.md

@@ -7,6 +7,10 @@ in 3.3 minor versions.
 To get the diff for a specific change, go to https://github.com/symfony/symfony/commit/XXX where XXX is the change hash
 To get the diff between two versions, go to https://github.com/symfony/symfony/compare/v3.3.0...v3.3.1
 
+* 3.3.8 (2017-08-28)
+
+ * bug #24016 [DI] Fix tracking env var placeholders nested in object graphs (nicolas-grekas)
+
 * 3.3.7 (2017-08-28)
 
  * bug #24009 [DI] Fix tracking env vars when merging configs (bis) (nicolas-grekas)