primitives: use generic Header in testing runtime (#6561)

* primitives: use generic Header in testing runtime

* frame: remove unused imports

* Remove warning

Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/frame/grandpa/src/mock.rs

@@ -40,8 +40,8 @@ use sp_runtime::{
 	impl_opaque_keys,
 	testing::{Header, TestXt, UintAuthorityId},
 	traits::{
-		Convert, Extrinsic as ExtrinsicT, Header as _, IdentityLookup, OpaqueKeys,
-		SaturatedConversion, SignedExtension,
+		Convert, Extrinsic as ExtrinsicT, IdentityLookup, OpaqueKeys, SaturatedConversion,
+		SignedExtension,
 	},
 	transaction_validity::TransactionValidityError,
 	DigestItem, Perbill,

substrate/frame/grandpa/src/tests.rs

@@ -30,7 +30,7 @@ use frame_support::{
 use frame_system::{EventRecord, Phase};
 use sp_core::H256;
 use sp_keyring::Ed25519Keyring;
-use sp_runtime::{testing::Digest, traits::Header};
+use sp_runtime::testing::Digest;
 
 #[test]
 fn authorities_change_logged() {