Remove `private_shop` configuration from Context generating a new app

[kennyadsl]

Overview/summary

Geneating a new app with shopify_app, we are copying the private_shop configuration in the setup.

Is this still needed? I couldn't find any documentation on in which cases this option makes sense to be used. If we can remove it, I can make a PR for that.

[matteodepalo]

Hi @kennyadsl, I'll check this with the team.