Switch to a standard codegen comment marker

[SpikesDivZero]

I was looking at the go generics options available today and noticed in the docs that this project seems to be using a header of:

// This file was automatically generated by genny.
// Any changes will be lost if this file is regenerated.
// see https://github.com/cheekybits/genny

As it were, this header format isn't usually recognized as machine-generated by common linters.

Would it be possible to switch to the community standard header format? Perhaps something like this:

// Code generated by genny - DO NOT EDIT.
// https://github.com/cheekybits/genny

This change would make it such that any linters could recognize that the code isn't human-edited/maintained, and automatically make the appropriate "ignore issues in this file" determination.

Thanks for writing up this tooling, and I hope you're having a fantastic day! :)