chore: effectively disableing delay buffer

[gzeoneth]

If isDelayBufferable is set to false, it is hard to re-enable without doing contract upgrade due to the flag is stored in an immutable for gas optimization. We temporarily disable delay buffer by using a large threshold value so that isSynced return true and will not require a delay proof when posting batches.

    function isSynced(
        BufferData storage self
    ) internal view returns (bool) {
        return block.number - self.prevBlockNumber <= self.threshold;
    }

the previous config for sepolia is not large enough because prevBlockNumber might be 0 after an upgrade