Update hex-literal version, simplify imports and remove unused dependencies (#2371)

substrate/core/executor/Cargo.toml

@@ -25,7 +25,7 @@ tiny-keccak = "1.4.2"
 [dev-dependencies]
 assert_matches = "1.1"
 wabt = "~0.7.4"
-hex-literal = "0.1.0"
+hex-literal = "0.2.0"
 
 [features]
 default = []

substrate/core/executor/src/wasm_executor.rs

@@ -897,7 +897,7 @@ mod tests {
 	use parity_codec::Encode;
 
 	use state_machine::TestExternalities;
-	use hex_literal::{hex, hex_impl};
+	use hex_literal::hex;
 	use primitives::map;
 
 	#[test]