refactor(@angular-devkit/schematics): deprecate isAction

Author: santoshyadavdev

packages/angular_devkit/schematics/src/sink/sink.ts

@@ -27,7 +27,6 @@ import {
   OverwriteFileAction,
   RenameFileAction,
   UnknownActionException,
-  isAction,
 } from '../tree/action';
 import { Tree } from '../tree/interface';
 

packages/angular_devkit/schematics/src/tree/action.ts

@@ -156,7 +156,9 @@ export function isContentAction(action: Action): action is CreateFileAction | Ov
   return action.kind == 'c' || action.kind == 'o';
 }
 
-
+/**
+ * @deprecated since version 11.0. not used anymore can be removed in future version.
+ */
 export function isAction(action: any): action is Action {  // tslint:disable-line:no-any
   const kind = action && action.kind;