fix(abigen): remove redundant index adjustment for many overloads

[mattsse]

Motivation

removes a redundant index increase when deriving aliases for overloaded functions

prior to this, many overloaded function would be expanded to

        HEVMCalls::ToString0(inner) =>,
        HEVMCalls::ToString2(inner) => ,
        HEVMCalls::ToString3(inner) => ,
        HEVMCalls::ToString4(inner) => ,

as seen here https://github.com/foundry-rs/foundry/pull/2127/files

Solution

removes the index increase that turned out to be redundant.

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog