fix: align ISwap interface to Swap implementation

[miguelmota]

@red-impala check out the v1 branch which is the current live implementation

https://github.com/hop-protocol/contracts/blob/8cefc3975115b6e3e706dd110670badad954a3bd/contracts/saddle/Swap.sol#L317

@cwhinfrey @shanefontaine wondering if we should default to v1 since it may be confusing

edit: was looking at the wrong file but the PR is still valid I think for v1 branch

[charlesndalton]

@miguelmota Ok, will create the PR on v1 since I see it has the same problem

[charlesndalton]

PR