cmd/go/internal/modfetch: correct TestCodeRepo expectation

cmd/go/internal/modfetch: correct TestCodeRepo expectation

The proxy protocol was simplified to only send
(and only receive) the Path and Version fields
in the JSON blob, not Name and Short.
(Those make sense when querying a VCS repo directly,
but not when talking about extracted modules.)
So don't expect them in the test.

Fixes #27042.

Change-Id: I3daacd668126e2227dcc8e6b89ee0cf0e3c8497c
Reviewed-on: https://go-review.googlesource.com/129684
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>