Enable treasury.spend by Root origin for Polkadot network before Gov2 (#6490)

* Enable treasury.spend by Root origin

* EnsureRoot -> EnsureRootWithSuccess

polkadot/runtime/polkadot/src/lib.rs

@@ -833,6 +833,7 @@ parameter_types! {
 	pub const MaxKeys: u32 = 10_000;
 	pub const MaxPeerInHeartbeats: u32 = 10_000;
 	pub const MaxPeerDataEncodingSize: u32 = 1_000;
+	pub const RootSpendOriginMaxAmount: Balance = Balance::MAX;
 }
 
 type ApproveOrigin = EitherOfDiverse<
@@ -856,7 +857,7 @@ impl pallet_treasury::Config for Runtime {
 	type SpendFunds = Bounties;
 	type MaxApprovals = MaxApprovals;
 	type WeightInfo = weights::pallet_treasury::WeightInfo<Runtime>;
-	type SpendOrigin = frame_support::traits::NeverEnsureOrigin<Balance>;
+	type SpendOrigin = frame_system::EnsureRootWithSuccess<AccountId, RootSpendOriginMaxAmount>;
 }
 
 parameter_types! {