x509roots/fallback/internal/goissue52287: delete

By now Go 1.19 isn't supported, so there's no need to work around
go.dev/issue/52287 in this module anymore.

For golang/go#57792.
For golang/go#52287.

Change-Id: I3999cdb9ca419a2ab897c9143a4ec31f59da7d80
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/598495
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>