pallet-balances may not be the only provider

[xlc]

substrate/frame/balances/src/lib.rs

Lines 1416 to 1419 in 0803f7d

	// TODO: This is over-conservative. There may now be other providers, and this pallet
	// may not even be a provider.
	let allow_death = existence_requirement == ExistenceRequirement::AllowDeath;
	let allow_death = allow_death && !system::Pallet::<T>::is_provider_required(transactor);

It should be using can_dec_provider instead of is_provider_required.

Also need to have some tests to cover the case where pallet-balances is not the only provider. Or if there are multiple instances of it.

[shaunxw]

I think it could be closed now with #9411 merged.