Incorrect BallotsTallied condition

[yuetloo]

Prerequisites

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• I am not running a deprecated version
• I checked the documentation and found no answer
• I checked to make sure that this issue has not already been filed

Expected Behavior

Please describe the behavior you are expecting

The condition to check if all ballots were tallied should be batchStartIndex >= numSignUps to account for the numSignUps === tallyBatchSize case.

For example, if tallyBatchSize = 25, and numSignUps = 25, the function will not emit the BallotsTallied event because (cachedBatchNum + 1) * tallyBatchSize = 25 which is not greater than 25.

https://github.com/privacy-scaling-explorations/maci/blob/dev/contracts/contracts/Tally.sol#L138-L140

    (uint8 intStateTreeDepth, , , ) = poll.treeDepths();
    uint256 tallyBatchSize = TREE_ARITY ** intStateTreeDepth;
    uint256 batchStartIndex = cachedBatchNum * tallyBatchSize;
    (uint256 numSignUps, ) = poll.numSignUpsAndMessages();

    // Require that there are untalied ballots left
    if (batchStartIndex > numSignUps) {
      revert AllBallotsTallied();
    }

https://github.com/privacy-scaling-explorations/maci/blob/dev/contracts/contracts/Tally.sol#L151-L153

    if ((cachedBatchNum + 1) * tallyBatchSize > numSignUps) {
      emit BallotsTallied(address(poll));
    }

Current Behavior

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Failure Information

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Context

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Failure Logs

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