Replace HOST env var with SHOPIFY_APP_URL?

[xmunoz]

https://github.com/Shopify/shopify-app-template-react-router/blob/main/vite.config.ts#L5

This comment suggests that this functionality should be deprecated in React Router 7 (which is the next version of Remix v2). However, I tried removing this and got an error. Is this comment still relevant? If not, how can we replace or remove this such that local dev environments can be successfully brought up?