remove bound on accountID in AssetFeeAsExistentialDepositMultiplier (#3303)

I dont think this bound is required by anything else and it allows now
to use this struct with runtimes that have 20 bytes accounts

---------

Co-authored-by: Bastian Köcher <git@kchr.de>

cumulus/parachains/common/src/xcm_config.rs

@@ -45,8 +45,6 @@ where
 		<Runtime as pallet_assets::Config<AssetInstance>>::AssetId,
 		<Runtime as pallet_assets::Config<AssetInstance>>::Balance,
 	>,
-	AccountIdOf<Runtime>:
-		From<polkadot_primitives::AccountId> + Into<polkadot_primitives::AccountId>,
 {
 	fn charge_weight_in_fungibles(
 		asset_id: <pallet_assets::Pallet<Runtime, AssetInstance> as Inspect<