Do not include :code in the storage proof if not required (#480)

This is basically a hack that prevents the inclusion of `:code` in the
storage proof. A proper fix requires some changes to the trie crate to
not include nodes that aren't read.

polkadot-parachains/statemine-runtime/src/lib.rs

@@ -672,7 +672,7 @@ construct_runtime!(
 	{
 		// System support stuff.
 		System: frame_system::{Pallet, Call, Config, Storage, Event<T>} = 0,
-		ParachainSystem: cumulus_pallet_parachain_system::{Pallet, Call, Storage, Inherent, Event<T>} = 1,
+		ParachainSystem: cumulus_pallet_parachain_system::{Pallet, Call, Config, Storage, Inherent, Event<T>} = 1,
 		RandomnessCollectiveFlip: pallet_randomness_collective_flip::{Pallet, Call, Storage} = 2,
 		Timestamp: pallet_timestamp::{Pallet, Call, Storage, Inherent} = 3,
 		ParachainInfo: parachain_info::{Pallet, Storage, Config} = 4,
@@ -734,8 +734,17 @@ pub type Executive = frame_executive::Executive<
 	frame_system::ChainContext<Runtime>,
 	Runtime,
 	AllPallets,
+	OnRuntimeUpgrade,
 >;
 
+pub struct OnRuntimeUpgrade;
+impl frame_support::traits::OnRuntimeUpgrade for OnRuntimeUpgrade {
+	fn on_runtime_upgrade() -> u64 {
+		sp_io::storage::set(b":c", &[]);
+		RocksDbWeight::get().writes(1)
+	}
+}
+
 impl_runtime_apis! {
 	impl sp_consensus_aura::AuraApi<Block, AuraId> for Runtime {
 		fn slot_duration() -> sp_consensus_aura::SlotDuration {