[dev.typeparams] runtime/race: make test compatible with types2

types2 correctly distinguishes variable assignment from use even
within function literals. Whatever the outcome of #3059, the test
cases in runtime/race need to be fixed to accomodate that.

Change-Id: Ibe3547f07b681ff41225caabaf050872a48c98d1
Reviewed-on: https://go-review.googlesource.com/c/go/+/325030


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