cmd/go/internal/modfetch: filter pseudo-versions from proxy /list endpoints
The /list files in the module cache include pseudo-versions, but the
documentation for (*modfetch).Repo.Versions explicitly states that
they are not included in the output of that method.
Fixes #32715
Change-Id: Ieba1500b91f52b5fa689e70e16dbe3ad40de20f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/183402
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>