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>

go.sum

@@ -46,8 +46,6 @@ filippo.io/edwards25519 v1.1.0 h1:FNf4tywRC1HmFuKW5xopWpigGjJKiJSV0Cqo0cJWDaA=
 filippo.io/edwards25519 v1.1.0/go.mod h1:BxyFTGdWcka3PhytdK4V28tE5sGfRvvvRV7EaN4VDT4=
 filippo.io/mkcert v1.4.4 h1:8eVbbwfVlaqUM7OwuftKc2nuYOoTDQWqsoXmzoXZdbc=
 filippo.io/mkcert v1.4.4/go.mod h1:VyvOchVuAye3BoUsPUOOofKygVwLV2KQMVFJNRq+1dA=
-fybrik.io/crdoc v0.6.3 h1:jNNAVINu8up5vrLa0jrV7z7HSlyHF/6lNOrAtrXwYlI=
-fybrik.io/crdoc v0.6.3/go.mod h1:kvZRt7VAzOyrmDpIqREtcKAVFSJYEBoAyniYebsJGtQ=
 github.com/Abirdcfly/dupword v0.0.11 h1:z6v8rMETchZXUIuHxYNmlUAuKuB21PeaSymTed16wgU=
 github.com/Abirdcfly/dupword v0.0.11/go.mod h1:wH8mVGuf3CP5fsBTkfWwwwKTjDnVVCxtU8d8rgeVYXA=
 github.com/AlekSi/pointer v1.2.0 h1:glcy/gc4h8HnG2Z3ZECSzZ1IX1x2JxRVuDzaJwQE0+w=