fix: Convert vendor/pezkuwi-subxt from submodule to regular directory

vendor/pezkuwi-subxt/subxt/src/book/usage/mod.rs

@@ -0,0 +1,27 @@
+// Copyright 2019-2025 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! This modules contains examples of using Subxt; follow the links for more:
+//!
+//! - [Transactions](transactions)
+//! - [Storage](storage)
+//! - [Events](events)
+//! - [Constants](constants)
+//! - [Blocks](blocks)
+//! - [Runtime APIs](runtime_apis)
+//! - [Unstable Light Client](light_client)
+//! - [Custom Values](custom_values)
+//! - [RPC calls](rpc)
+//!
+//! Alternately, [go back](super).
+
+pub mod blocks;
+pub mod constants;
+pub mod custom_values;
+pub mod events;
+pub mod light_client;
+pub mod rpc;
+pub mod runtime_apis;
+pub mod storage;
+pub mod transactions;