Duplicated fields of `userOp.paymasterPostOpGasLimit` and `paymasterData.postOpGas`

In the current `master` branch, it seems that `userOp.paymasterPostOpGasLimit` and `paymasterData.postOpGas` are duplicated, because `userOp.paymasterPostOpGasLimit` and `paymasterData.postOpGas` are both added in the signature hash, and the wallet backend must use the exact suggested value of `paymasterPostOpGasLimit` returned by paymaster through [ERC-7677](https://eips.ethereum.org/EIPS/eip-7677). There's no need to use `paymasterData.postOpGas` and add extra validity checks such as https://github.com/coinbase/verifying-paymaster/blob/6bee4b9161962dd5accbad15999c732b607bc3fa/src/VerifyingPaymaster.sol#L275-L278 anymore.