fix(@embark/demo): fix ethereum not available in browser in the demo
fix(@embark/demo): fix ethereum not available in browser in the demo

This only affected the demo. We somehow put the `enableEthereum()`
call right before the Demo `set` function, so since we now throw
when it's not available, it stopped the `set`. But it was never
needed because demo has `autoEnadble` on, meaning that `enable` is
called at the start.

iurimatias/embark-framework,iurimatias/embark-framework