update SidecarContainers to stable in v1.33 (#49685)

* update SidecarContainers to stable in v1.33

* Update content/en/docs/reference/command-line-tools-reference/feature-gates/SidecarContainers.md

Co-authored-by: Dipesh Rawat <rawat.dipesh@gmail.com>

---------

Co-authored-by: Dipesh Rawat <rawat.dipesh@gmail.com>

Author: pacoxu

content/en/docs/concepts/workloads/pods/_index.md

@@ -374,7 +374,7 @@ By default, init containers run and complete before the app containers are start
 You can also have [sidecar containers](/docs/concepts/workloads/pods/sidecar-containers/)
 that provide auxiliary services to the main application Pod (for example: a service mesh).
 
-{{< feature-state for_k8s_version="v1.29" state="beta" >}}
+{{< feature-state feature_gate_name="SidecarContainers" >}}
 
 Enabled by default, the `SidecarContainers` [feature gate](/docs/reference/command-line-tools-reference/feature-gates/)
 allows you to specify `restartPolicy: Always` for init containers.

content/en/docs/reference/command-line-tools-reference/feature-gates/SidecarContainers.md

@@ -13,6 +13,10 @@ stages:
   - stage: beta
     defaultValue: true
     fromVersion: "1.29"
+    toVersion: "1.32"
+  - stage: stable
+    defaultValue: true
+    fromVersion: "1.33"
 ---
 Allow setting the `restartPolicy` of an init container to
 `Always` so that the container becomes a sidecar container (restartable init containers).