Remove initial modal from onboarding

[hstove]

Right now, the onboarding flow in the app includes the first modal, which is intended to be included only on the app before opening the popup.

We need to remove this from the app, and instead include it in @blockstack/connect. The first screen in this app should be the screen that comes after "Create Data Vault". Or, if "Sign in instead" is selected, then the sign in flow should show up right away.