[release-branch.go1.23] revert "go/types, types2: only use fileVersion if 1.21 or...

[release-branch.go1.23] revert "go/types, types2: only use fileVersion if 1.21 or greater"

This reverts commit CL 604935.

Reason for revert: The team has decided that this change will be added to a point release.

Change-Id: I1c1032b881c3a98312a4753b9767cb7c8eed9e09
Reviewed-on: https://go-review.googlesource.com/c/go/+/605096
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>