Part 2

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Unnecessary update of available USDC of engine's usd token

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In `CreditDelegationBranch::settleVaultsDebt`, the `if()` get executed when the vault is in debt(less USDC than vault asset),

that is, vault unsettled realized debt in USD is less than zero then the exact amount of USDC needed to pay for the debt is

calculated and part of the vault assets is converted to USDC to cover for vault debts.

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The exact USDC gotten is used to update(pay) debt of the vault and no USDC will be remained since the exact amount needed was

calculated in

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ctx.swapAmount = calculateSwapAmount(

dexSwapStrategy.dexAdapter,

ctx.usdc,

ctx.vaultAsset,

usdcCollateralConfig.convertSd59x18ToTokenAmount(ctx.vaultUnsettledRealizedDebtUsdX18.abs()),

);

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However, the line of code below is not needed because the USDC gotten from the swap was used up to pay the debt. Moreover,

the NatSpec of `usdcAvailableForEngine` in `UsdTokenSwapConfig` says "The amount of USDC backing an engine's usd token,

coming from vaults that had their debt settled, allocating the usdc acquired to users of that engine." meaning only vault

with debt can store USDC using this mapping which is not the case for `if()` of `CreditDelegationBranch::settleVaultsDebt`.

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@> UsdTokenSwapConfig.load().usdcAvailableForEngine[vault.engine] += ctx.usdcOutX18.intoUint256();

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`vault.engine` will have more USDC than its balance since the USDC from swapped was used for debt settlement.

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Remove the line of code

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- UsdTokenSwapConfig.load().usdcAvailableForEngine[vault.engine] += ctx.usdcOutX18.intoUint256();