Add some trivial improvements to primitives runtime (#8528)

* Add some trivial improvements

* Finish primitives/runtime

substrate/primitives/runtime/src/generic/header.rs

@@ -91,7 +91,7 @@ impl<Number, Hash> Decode for Header<Number, Hash> where
 	Hash::Output: Decode,
 {
 	fn decode<I: Input>(input: &mut I) -> Result<Self, Error> {
-		Ok(Header {
+		Ok(Self {
 			parent_hash: Decode::decode(input)?,
 			number: <<Number as HasCompact>::Type>::decode(input)?.into(),
 			state_root: Decode::decode(input)?,
@@ -160,7 +160,7 @@ impl<Number, Hash> traits::Header for Header<Number, Hash> where
 		parent_hash: Self::Hash,
 		digest: Digest<Self::Hash>,
 	) -> Self {
-		Header {
+		Self {
 			number,
 			extrinsics_root,
 			state_root,