[dev.typeparams] cmd/go: relax test expectation

go/types reports `"pkg/path" imported and not used` rather than
`imported and not used: "pkg/path"`, like cmd/compile. Relax the test
expectation to accomodate either.

Change-Id: I318992946160a9090f8991f4c97784ba1d1b78b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/282913


Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>