cmd/k8s-operator,tstest,go.{mod,sum}: remove fybrik.io/crdoc dependency (#12862)

Remove fybrik.io/crdoc dependency as it is causing issues for folks attempting
to vendor tailscale using GOPROXY=direct.
This means that the CRD API docs in ./k8s-operator/api.md will no longer
be generated- I am going to look at replacing it with another tool
in a follow-up.

Updates tailscale/tailscale#12859

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

tstest/tools/tools.go

@@ -8,7 +8,6 @@
 package tools
 
 import (
-	_ "fybrik.io/crdoc"
 	_ "github.com/tailscale/mkctr"
 	_ "honnef.co/go/tools/cmd/staticcheck"
 	_ "sigs.k8s.io/controller-tools/cmd/controller-gen"