Convert all UK spelling to US (#2138)

* all the ise

* forgot a misspelling

* a few more replacements

* bump impl

* rollback and fixes

* bump impl again

* Add aliases for RPC

* Update on_demand.rs

substrate/core/network/src/message.rs

@@ -66,7 +66,7 @@ pub type BlockResponse<B> = generic::BlockResponse<
 /// A set of transactions.
 pub type Transactions<E> = Vec<E>;
 
-/// Bits of block data and associated artefacts to request.
+/// Bits of block data and associated artifacts to request.
 bitflags! {
 	/// Node roles bitmask.
 	pub struct BlockAttributes: u8 {