go/types, types2: remove version check for more lenient constant handling in inference

go/types, types2: remove version check for more lenient constant handling in inference

For #58671.
Fixes #60566.

Change-Id: I746f99cdfd44b204dc90350fcfb3867e9b8b1da8
Reviewed-on: https://go-review.googlesource.com/c/go/+/499997
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>