go/types, types2: always accept type parameters when running Manual test
This makes it easier to run tests on existing generic code that is
not using the `.go2` ending currently used by type checker tests.
For #49074.
Change-Id: I1501463c55dbe1d709918786e1a43b6d1bf1629a
Reviewed-on: https://go-review.googlesource.com/c/go/+/357050
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>