solana: Remove references to `payer.sequence_value` from the code comments

[johnsaigle]

This value was removed in #90 but is still listed as the seed for PDAs in e.g.

example-liquidity-layer/solana/programs/token-router/src/processor/market_order/place_cctp.rs

Lines 90 to 110 in f9d747b

	/// CHECK: Mutable. Seeds must be \["core-msg", payer, payer_sequence.value\].
	#[account(
	mut,
	seeds = [
	common::CORE_MESSAGE_SEED_PREFIX,
	prepared_order.key().as_ref(),
	],
	bump,
	)]
	core_message: UncheckedAccount<'info>,
	/// CHECK: Mutable. Seeds must be \["cctp-msg", payer, payer_sequence.value\].
	#[account(
	mut,
	seeds = [
	common::CCTP_MESSAGE_SEED_PREFIX,
	prepared_order.key().as_ref(),
	],
	bump,
	)]
	cctp_message: UncheckedAccount<'info>,