KubernetesGateway provider out of experimental

Co-authored-by: Kevin Pollet <pollet.kevin@gmail.com>

docs/content/migration/v3.md

@@ -25,3 +25,29 @@ the `endpoints` right has to be removed and the following `endpointslices` right
       - watch
   ...
 ```
+
+#### Gateway API: KubernetesGateway Provider
+
+In v3.1, the KubernetesGateway Provider is no longer an experimental feature.
+It can be enabled without the associated `experimental.kubernetesgateway` option, which is now deprecated.
+
+??? example "An example of the experimental `kubernetesgateway` option"
+
+    ```yaml tab="File (YAML)"
+    experimental:
+      kubernetesgateway: true
+    ```
+
+    ```toml tab="File (TOML)"
+    [experimental]
+        kubernetesgateway=true
+    ```
+
+    ```bash tab="CLI"
+    --experimental.kubernetesgateway=true
+    ```
+
+##### Remediation
+
+The `kubernetesgateway` option should be removed from the experimental section of the static configuration.
+To configure `kubernetesgateway`, please check out the [KubernetesGateway Provider documentation](../providers/kubernetes-gateway.md).

docs/content/reference/static-configuration/cli-ref.md

@@ -211,7 +211,7 @@ WriteTimeout is the maximum duration before timing out writes of the response. I
 Timeout defines how long to wait on an idle session before releasing the related resources. (Default: ```3```)
 
 `--experimental.kubernetesgateway`:  
-Allow the Kubernetes gateway api provider usage. (Default: ```false```)
+(Deprecated) Allow the Kubernetes gateway api provider usage. (Default: ```false```)
 
 `--experimental.localplugins.<name>`:  
 Local plugins configuration. (Default: ```false```)

docs/content/reference/static-configuration/env-ref.md

@@ -211,7 +211,7 @@ WriteTimeout is the maximum duration before timing out writes of the response. I
 Timeout defines how long to wait on an idle session before releasing the related resources. (Default: ```3```)
 
 `TRAEFIK_EXPERIMENTAL_KUBERNETESGATEWAY`:  
-Allow the Kubernetes gateway api provider usage. (Default: ```false```)
+(Deprecated) Allow the Kubernetes gateway api provider usage. (Default: ```false```)
 
 `TRAEFIK_EXPERIMENTAL_LOCALPLUGINS_<NAME>`:  
 Local plugins configuration. (Default: ```false```)