Snaps: Update screenshots on Notifications feature page to match v12 UX

[Montoya]

This page: https://docs.metamask.io/snaps/features/notifications

will need to be updated to match the UX of v12

[subhamkumarr]

@Montoya, is this the correct screenshot demo to replace?

[Montoya]

There's a lot more to update. It will be easier to do it when v12 of the MetaMask Extension goes live.

[subhamkumarr]

OK

[alexandratran]

Fixed by #1533