doc: remove persist crate from README

Author: luisschwab

README.md

@@ -37,7 +37,6 @@ The project is split up into several crates in the `/crates` directory:
 
 - [`wallet`](./crates/wallet): Contains the central high level `Wallet` type that is built from the low-level mechanisms provided by the other components
 - [`chain`](./crates/chain): Tools for storing and indexing chain data
-- [`persist`](./crates/persist): Types that define data persistence of a BDK wallet
 - [`file_store`](./crates/file_store): Persistence backend for storing chain data in a single file. Intended for testing and development purposes, not for production.
 - [`esplora`](./crates/esplora): Extends the [`esplora-client`] crate with methods to fetch chain data from an esplora HTTP server in the form that [`bdk_chain`] and `Wallet` can consume.
 - [`electrum`](./crates/electrum): Extends the [`electrum-client`] crate with methods to fetch chain data from an electrum server in the form that [`bdk_chain`] and `Wallet` can consume.