Fix wallet standard docs URL (MystenLabs#15318)

## Description 

Noticed this was linking to a dead URL.

## Test Plan 

How did you test the new or updated feature?

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

sdk/wallet-standard/README.md

@@ -3,4 +3,4 @@
 A suite of standard utilities for implementing wallets and libraries based on the
 [Wallet Standard](https://github.com/wallet-standard/wallet-standard/).
 
-**Documentation:** https://sdk.mystenlabs.com/dapp-kit/wallet-standard
+**Documentation:** https://docs.sui.io/standards/wallet-standard