[program] Remove an overly strict validation check on withheld fee destination account

[samkim-crypto]

Problem

The WithdrawWithheldTokensFromMint instruction credits tokens directly to the available balance of the destination account and does not update the pending balance or its associated credit counter. Therefore, the instruction should not fail when the destination account’s pending_balance_credit_counter equals its maximum_pending_balance_credit_counter, since no pending credit is created.

Applying this check incorrectly leads to unnecessary transaction failures and can prevent the TransferFeeConfig withdraw-withheld authority from distributing withheld fees to certain accounts. Moreover, because this authority cannot invoke ApplyPendingBalance on accounts it does not own, it has no way to reduce their pending_balance_credit_counter, meaning such accounts may be permanently unable to receive withheld-fee withdrawals even though the operation is semantically valid.

Summary of Changes

Remove the overly strict validation check on withheld fee destination account.

[joncinque]

Looks great!