Fix compilation on latest nightly because of stdsimd (#3296)

We need to bump `ahash` to make it compile again.

Closes: https://github.com/paritytech/polkadot-sdk/issues/3269

substrate/bin/node-template/env-setup/README.md

@@ -0,0 +1,9 @@
+# Env setup
+
+Special files for setting up an environment to work with the template:
+
+- `rust-toolchain.toml` when working with `rustup`.
+- `flake.nix` when working with `nix`.
+
+These files will be copied by the installer script to the main directory. They are
+put into this special directory to not interfere with the normal CI.

substrate/bin/node-template/env-setup/rust-toolchain.toml

@@ -1,5 +1,5 @@
 [toolchain]
-channel = "nightly"
+channel = "stable"
 components = [
 	"cargo",
 	"clippy",