Fix diagram link

Author: steinybot

README.md

@@ -43,7 +43,7 @@ Main o-- A
 @enduml
 ```
 
-![Example Class Diagram](http://www.plantuml.com/plantuml/proxy?cache=no&src=https://raw.github.com/BotTech/scala2plantuml/main/example/example.md)
+![Example Class Diagram](http://www.plantuml.com/plantuml/proxy?cache=no&src=https://raw.githubusercontent.com/BotTech/scala2plantuml/main/example/example.md)
 
 ## sbt