Remove Unused AccountIndex (#9149)

* remove unused `AccountIndex`

* Update lib.rs

substrate/bin/node-template/runtime/src/lib.rs

@@ -52,10 +52,6 @@ pub type Signature = MultiSignature;
 /// to the public key of our transaction signing scheme.
 pub type AccountId = <<Signature as Verify>::Signer as IdentifyAccount>::AccountId;
 
-/// The type for looking up accounts. We don't expect more than 4 billion of them, but you
-/// never know...
-pub type AccountIndex = u32;
-
 /// Balance of an account.
 pub type Balance = u128;
 
@@ -65,9 +61,6 @@ pub type Index = u32;
 /// A hash of some data used by the chain.
 pub type Hash = sp_core::H256;
 
-/// Digest item type.
-pub type DigestItem = generic::DigestItem<Hash>;
-
 /// Opaque types. These are used by the CLI to instantiate machinery that don't need to know
 /// the specifics of the runtime. They can then be made to be agnostic over specific formats
 /// of data like extrinsics, allowing for them to continue syncing the network through upgrades