Remove redundant currentTime variable in SignedExclusiveSwap

[Copilot]

currentTime was redundantly assigned uint32(block.timestamp) mid-function when currentTimestamp already held the same value from earlier in the same call.

Change

• Removed uint32 currentTime = uint32(block.timestamp) and replaced all usages with the existing currentTimestamp variable throughout the fee accumulation block.

// Before
uint32 currentTimestamp = uint32(block.timestamp);
// ... signature/deadline checks using currentTimestamp ...
uint32 currentTime = uint32(block.timestamp); // redundant
if (state.lastUpdateTime() != currentTime) {
    ...
    state = state.withLastUpdateTime(currentTime);
}

// After
uint32 currentTimestamp = uint32(block.timestamp);
// ... signature/deadline checks ...
if (state.lastUpdateTime() != currentTimestamp) {
    ...
    state = state.withLastUpdateTime(currentTimestamp);
}

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