Don't require go mod tidy
Created by: felixfbecker
According to the Go modules FAQ it is intentional and beneficial that old entries are kept around: https://github.com/golang/go/wiki/Modules#is-gosum-a-lock-file-why-does-gosum-include-information-for-module-versions-i-am-no-longer-using
Renovate does not run go mod tidy
after updating, at least not until https://github.com/renovatebot/renovate/issues/2594 adds an option, so this currently blocks us from using Renovate.
We can add it back later if we want once Renovate has the option, or decide the Go team knows best