use https instead of http for the iframe sample App.

:koala: :+1: 

Lotus is through https. Current iframe sample App has http://wikipedia.com as source. If upload the zip to an account on the production server, wikipedia page won't show up in iframe by default. User has to enable unsafe script.

Hence, I am changing the iframe source to https://www.wikipedia.org.

/cc @jwswj @maximeprades @zendesk/quokka @princemaple