cmd/go: fix fips doc link

Change-Id: I8f06ebd65ba9961e19274c1e5fec251b18395d1c
Reviewed-on: https://go-review.googlesource.com/c/go/+/691435
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Sean Liao <sean@liao.dev>
Auto-Submit: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: rolandshoemaker

src/cmd/go/alldocs.go

@@ -695,7 +695,7 @@ Special-purpose environment variables:
 		The default is GOFIPS140=off, which makes no FIPS-140 changes at all.
 		Other values enable FIPS-140 compliance measures and select alternate
 		versions of the cryptography source code.
-		See https://go.dev/security/fips140 for details.
+		See https://go.dev/doc/security/fips140 for details.
 	GO_EXTLINK_ENABLED
 		Whether the linker should use external linking mode
 		when using -linkmode=auto with code that uses cgo.