Gh pages remove bootstrap js

@zackbloom we don't need this here anymore, correct?

Note: I already removed bootstrap styles with https://github.com/HubSpot/messenger/commit/541645aeacafedc4d8fd5f132a5aa9139243ad3e and https://github.com/HubSpot/messenger/commit/b90ac8b54427e1984f77abdf69731ac21e98490c.