Fixes for chapter 5 (Ledger Rules and Fraud Proofs)

[mpetruska]

• fix uncovered typos
• ready for review/merge

[keyan-m]

@mpetruska this is actually great timing. With withdrawal events now being optimistic and structured as below:

midgard/onchain/aiken/lib/midgard/ledger-state.ak

Lines 112 to 147 in 6f10f04

	// ### Withdrawal event
	pub type WithdrawalId =
	OutputReference
	pub type WithdrawalBody {
	l2_outref: OutputReference,
	l2_owner: VerificationKeyHash,
	l2_value: ValuePairs,
	l1_address: Address,
	l1_datum: CardanoDatum,
	}
	pub type WithdrawalSignature =
	Pair<VerificationKey, Signature>
	pub type WithdrawalValidity {
	WithdrawalIsValid
	NonExistentWithdrawalUtxo
	SpentWithdrawalUtxo { l2_tx_hash: H32<MidgardTxCompact> }
	IncorrectWithdrawalOwner
	IncorrectWithdrawalValue
	IncorrectWithdrawalSignature
	TooManyTokensInWithdrawal
	}
	pub type WithdrawalInfo {
	body: WithdrawalBody,
	signature: WithdrawalSignature,
	validity: WithdrawalValidity,
	}
	pub type WithdrawalEvent {
	id: WithdrawalId,
	info: WithdrawalInfo,
	}

Do you think this implementation is sufficient for adding corresponding fraud proofs in the specs? How sensible/practical would it be to pursue proving exhaustiveness of the possible invalidity claims?