Revert "Fix serialization of transaction_paymentInfo" (#4166)

* Revert "Fix serialization of `transaction_paymentInfo` (#4146)"

This reverts commit 613b5e7e2d.

* Revert chain-spec too.

* Bring back camelCase and test.

substrate/palette/transaction-payment/rpc/runtime-api/Cargo.toml

@@ -12,7 +12,7 @@ rstd = { package = "sr-std", path = "../../../../primitives/sr-std", default-fea
 sr-primitives = { path = "../../../../primitives/sr-primitives", default-features = false }
 
 [dev-dependencies]
-serde_json = { version = "1.0.41", features = ["arbitrary_precision"] }
+serde_json = "1.0.41"
 
 [features]
 default = ["std"]

substrate/palette/transaction-payment/rpc/runtime-api/src/lib.rs

@@ -52,11 +52,11 @@ mod tests {
 	use super::*;
 
 	#[test]
-	fn should_serialize_properly_with_u128() {
+	fn should_serialize_properly_with_u64() {
 		let info = RuntimeDispatchInfo {
 			weight: 5,
 			class: DispatchClass::Normal,
-			partial_fee: 1_000_000_u128,
+			partial_fee: 1_000_000_u64,
 		};
 
 		assert_eq!(