beta site: improve install hint placing

[tooomm]

The install hint Make sure to follow the setup guide before installing placement could be improved within the app info pages for better visibility and logical structure:

• On the right of the Install button or directly below it, not below the picture:
  

• Above the instructions since a user has to check that first :)
  

[TingPing]

Beta site issues are handled here: https://github.com/flathub/linux-store-frontend