cmd/go: handle '@' in local path when running 'go mod edit -replace'

cmd/go: handle '@' in local path when running 'go mod edit -replace'

The existing implementation considers everything after '@' as a version.

Fixes #61500

Change-Id: I72c32529c2726c2b59c089f5ffd6a2e361ef2c65
Reviewed-on: https://go-review.googlesource.com/c/go/+/538916
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>