Demo app hyperswitch-demo-store.netlify.app of sandbox to point to app.hyperswitch.io/api backend

[akash-c-k]

~~Current Demo app is pointing to sandbox.hyperswitch.io for backend api calls, which has to be replaced with app.hyperswitch.io/api example, sandbox.hyperswitch.io/health will from now be app.hyperswitch.io/api/health~~

This will be done via infra level mapping via @inventvenkat