Update AMBBridgeHelper.sol

[0xScratch]

Changed uint256 i = 0 to uint256 i, there's no need to initialize some 'uint' variable to 0 cuz the default value already sets itself to 0. Saves some gas too.

Moreover, there's one more change we can make in this 'for' loop, that is changing i++ to ++i, if this change isn't messing up with the code logic, This is always beneficial to do so. Although, I haven't made this change, just a suggestion if you are down with it!