add a comment to InTreePluginPortworxUnregister

Author: carlory

pkg/features/versioned_kube_features.go

@@ -417,7 +417,7 @@ var defaultVersionedKubernetesFeatureGates = map[featuregate.Feature]featuregate
 	},
 
 	InTreePluginPortworxUnregister: {
-		{Version: version.MustParse("1.23"), Default: false, PreRelease: featuregate.Alpha},
+		{Version: version.MustParse("1.23"), Default: false, PreRelease: featuregate.Alpha}, // remove it along with CSIMigrationPortworx in 1.36
 	},
 
 	JobBackoffLimitPerIndex: {