Promote image CLI commands to stable

Remove experimental status from flux image commands in preparation
for GA release of image automation APIs.

Partial fix for #5411

Signed-off-by: Daniel Guns <danbguns@gmail.com>

cmd/flux/get_image_policy.go

@@ -28,7 +28,7 @@ import (
 var getImagePolicyCmd = &cobra.Command{
 	Use:   "policy",
 	Short: "Get ImagePolicy status",
-	Long:  withPreviewNote("The get image policy command prints the status of ImagePolicy objects."),
+	Long:  "The get image policy command prints the status of ImagePolicy objects.",
 	Example: `  # List all image policies and their status
   flux get image policy