Update develop to patch-polkadot-sdk

Allows us to finally remove the old `serai-dex/substrate` repository _and_
should have CI pass without issue on `develop` again.

The changes made here should be trivial and maintain all prior
behavior/functionality. The most notable are to `chain_spec.rs`, in order to
still use a SCALE-encoded `GenesisConfig` (avoiding `serde_json`).

tests/processor/src/networks.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)]
+
 use zeroize::Zeroizing;
 use rand_core::{RngCore, OsRng};