Upgrade to polkadot-v1.7.1

Upgrade note:

• MaxHold was deleted from pallet_balances.

To do:

• Upgrade duniter-polkadot-sdk.
• Upgrade duniter subxt.
• Upgrade node.

pallets/distance/src/mock.rs

@@ -200,7 +200,6 @@ impl pallet_balances::Config for Test {
     type ExistentialDeposit = ExistentialDeposit;
     type FreezeIdentifier = ();
     type MaxFreezes = ConstU32<0>;
-    type MaxHolds = ConstU32<0>;
     type MaxLocks = MaxLocks;
     type MaxReserves = ();
     type ReserveIdentifier = [u8; 8];