Remove and ignore go workspace files

[squaremo]

There's no watertight advice on whether to check go workspace files in (go.work and go.work.sum), but generally they are regarded as local. See https://github.com/golang/go/issues/53502 as the most central discussion on this).

Here, they tend to get in the way, because go.work.sum is not updated by go mod tidy and isn't subject to (the default) -mod readonly. In the absence of a clear benefit to checking them in, I'm removing them.

[squaremo]

Thank you for reviewing this Max :bow: I meant to include .gitignore -- corrected.