docs(meshpassthrough): update support for gateway (#2094)

Signed-off-by: Lukasz Dziedziak <lukidzi@gmail.com>

app/_src/policies/meshpassthrough.md

@@ -17,6 +17,13 @@ When using this policy, the [passthrough mode](/docs/{{ page.release }}/networki
 | --------------------- | --------------------- |
 | `targetRef.kind`      | `Mesh`, `MeshSubset`  |
 {% endtab %}
+{% if_version gte:2.9.x %}
+{% tab targetRef Delegated Gateway %}
+| `targetRef`             | Allowed kinds        |
+| ----------------------- | -------------------- |
+| `targetRef.kind`        | `Mesh`, `MeshSubset` |
+{% endtab %}
+{% endif_version %}
 {% endtabs %}
 
 To learn more about the information in this table, see the [matching docs](/docs/{{ page.release }}/policies/introduction).
@@ -85,7 +92,7 @@ If you rely on tags in the top-level `targetRef` you might consider securing the
 
 * Due to the nature of some traffic, it is not possible to combine certain protocols on the same port. You can create a `MeshPassthrough` policy that handles `tcp`, `tls`, and one of `http`, `http2`, or `grpc` traffic on the same port. Layer 7 protocols cannot be distinguished, which could introduce unexpected behavior.
 * It is currently not possible to route passthrough traffic through the [zone egress](/docs/{{ page.release }}/production/cp-deployment/zoneegress/#zone-egress). However, this feature will be implemented in the future.
-* Gateways are currently not supported.
+* {% if_version gte:2.9.x %}Builtin gateway is not supported.{% endif_version %}{% if_version lte:2.8.x %}Gateways are currently not supported.{% endif_version %}
 
 ## Examples