thiserror annotations + spelling (#3452)

* remove duplicate thiserror annotations

* chore: cargo spellcheck

polkadot/node/core/approval-voting/src/criteria.rs

@@ -437,7 +437,7 @@ impl std::error::Error for InvalidAssignment { }
 ///   * Validator is present in backing group.
 ///
 /// This function does not check whether the core is actually a valid assignment or not. That should be done
-/// outside of the scope of this function.
+/// outside the scope of this function.
 pub(crate) fn check_assignment_cert(
 	claimed_core_index: CoreIndex,
 	validator_index: ValidatorIndex,

polkadot/node/core/chain-selection/src/backend.rs

@@ -45,7 +45,7 @@ pub(super) trait Backend {
 	fn load_leaves(&self) -> Result<LeafEntrySet, Error>;
 	/// Load the stagnant list at the given timestamp.
 	fn load_stagnant_at(&self, timestamp: Timestamp) -> Result<Vec<Hash>, Error>;
-	/// Load all stagnant lists up to and including the given unix timestamp
+	/// Load all stagnant lists up to and including the given UNIX timestamp
 	/// in ascending order.
 	fn load_stagnant_at_up_to(&self, up_to: Timestamp)
 		-> Result<Vec<(Timestamp, Vec<Hash>)>, Error>;