Update Changelog forgot the release date

dregad · dregad · commit 874178135a1f · 2020-05-19T20:13:08.000+02:00
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
@@ -10,7 +10,7 @@ specification.
 
 # Releases for MantisBT 2.x
 
-## [2.4.0]
+## [2.4.0] - 2020-05-19
 
 ### Added
 
