[docs] Don't document entryPoint in exp.json.
[docs] Don't document entryPoint in exp.json.

We're probably going to move the templates to a default component export, like CRNA. In that world we'll want to fully control the RN entry point, and this would only be used by very advanced users.

exponentjs/exponent,exponentjs/exponent,exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent,exponent/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent