docs(vpa): Label `InPlaceOrRecreate` mode as an `alpha feature` in `quick start` guide

This commit adds a dedicated `alpha feature` suffix to `InPlaceOrRecreate`
updateMode to indicate that the option is not available by default and
requires additional setup to enable it.

Also:
- Include reference to the `features.md` documentation to bring
  additional context to the reader and point them to the feature
  details.

vertical-pod-autoscaler/docs/quickstart.md

@@ -22,9 +22,10 @@ There are five modes in which *VPAs* operate:
   from the new recommendation (respecting the Pod Disruption Budget, if defined).
   This mode should be used rarely, only if you need to ensure that the pods are restarted
   whenever the resource request changes.
-- `"InPlaceOrRecreate"`: VPA assigns resource requests on pod creation as well as updates
+- `"InPlaceOrRecreate"`[__alpha feature__]: VPA assigns resource requests on pod creation as well as updates
   them on existing pods by leveraging [Kubernetes `in-place` update](https://kubernetes.io/blog/2025/05/16/kubernetes-v1-33-in-place-pod-resize-beta/) capability.
   If `in-place` update fails, it falls back to evicting the pods, performing a _recreation_.
+  For more details, see the [In-Place Updates documentation](https://github.com/kubernetes/autoscaler/blob/master/vertical-pod-autoscaler/docs/features.md#in-place-updates-inplaceorrecreate).
 - `"Initial"`: VPA only assigns resource requests on pod creation and never changes them
   later.
 - `"Off"`: VPA does not automatically change the resource requirements of the pods.