[Edit docs] Change references to Hiro Wallet to Leather Wallet

[AshtonStephens]

URL of the page to change: https://docs.stacks.co/docs/tutorials/hello-stacks

---

This page references Hiro Wallet but the wallet has been rebranded to Leather Wallet. This is the only page I've read so I bet there are other occurrences as well.

IMO it's probably sufficient to find and replace instances of Hiro wallet with Leather wallet in the docs and update the first instance of Hiro wallet in each page with Leather wallet (formerly Hiro wallet) to avoid confusion.

[AshtonStephens]

Also I suppose this bit under Wallet Setup is technically wrong because the wallet app is owned by Trust Machines:

... visit Hiro's wallet page and install it. ...