Update Leon Barnard author image reference

Author: annegentle

_data/authors.yml

@@ -23,7 +23,7 @@ jennifer_rondeau:
 
 leon_barnard:
   name: Leon Barnard
-  picture: https://media.balsamiq.com/img/company/team/2017/bio/leon.jpg
+  picture: https://docslikecode.com/images/leon.jpg
   github: //github.com/balsamiqLeon
   twitter: leonbarnard
   bio: "Designer and Writer"