[release-1.17] Minimum required Go version in go.mod is 1.20, which isn't enough

[debarshiray]

Commits fa5a4ac499d7327b and aa946f3f59c82c58 started using the slices package in Git main and release-1.17, which was only introduced in Go 1.21. Since then, main has been changed to require Go 1.22, but release-1.17 still only specifies Go 1.20 in go.mod.

It might be a good idea to make the Go version specified in go.mod match reality.