Update changelog for v4.1.1.

Author: Robert Jackson

CHANGELOG.md

@@ -1,3 +1,11 @@
+## v4.1.1 (2020-05-21)
+
+#### :bug: Bug Fix
+* [#210](https://github.com/ember-cli/ember-cli-version-checker/pull/210) [v4] Fix hasSingleImplementation ([@xg-wang](https://github.com/xg-wang))
+
+#### Committers: 1
+- Thomas Wang ([@xg-wang](https://github.com/xg-wang))
+-
 ##  v4.1.0 (2020-01-17)
 
 #### :rocket: Enhancement