crypto/internal/fips140/check: remove Enabled

crypto/internal/fips140/check: remove Enabled

check.Enabled, internal/fips140.Enabled, and crypto/fips140.Enabled were
redundant. Package check can just use internal/fips140.Enabled.

check.Verified is still there for the tests and belt-and-suspenders
assurance in crypto/fips140.Enabled, although it's implied by Enabled.

For #69536

Change-Id: I83921cc925da841aba4da79a9a5e9ac526a3f2bf
Reviewed-on: https://go-review.googlesource.com/c/go/+/638855
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>