Making the demo runnable offline
Revert "Update docs for running demo behind proxy"

This reverts commit f052131d7741eee21612959d88c2da4cca6ac0c4.

The previous commit (3bd1f7305d405a21603a973f0e100f39fd96c1f2) makes
the demo runnable offline, so there's no need to describe the use of
proxies