bin/lesson_initialize.py: Remove 'example-site' reference

The consumer was removed by 079d7d5 (Updating contribution guidelines
in boilerplate, 2016-06-26).

Author: wking

bin/lesson_initialize.py

@@ -158,7 +158,6 @@
 [dc-lessons]: http://datacarpentry.org/lessons/
 [dc-site]: http://datacarpentry.org/
 [discuss-list]: http://lists.software-carpentry.org/listinfo/discuss
-[example-site]: https://swcarpentry.github.io/lesson-example/
 [github]: http://github.com
 [github-flow]: https://guides.github.com/introduction/flow/
 [github-join]: https://github.com/join