Adding privacy disclaimer to Copilot Chat (microsoft#1154)

### Motivation and Context
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This PR adds UX disclaimer to Copilot Chat to meet Microsoft privacy
obligations for using Co-pilot internally on our team.

### Description
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Also cleans up unused properties in state

samples/apps/copilot-chat-app/webapp/src/redux/features/app/AppState.ts

@@ -3,8 +3,6 @@ import { AlertType } from '../../../libs/models/AlertType';
 // Copyright (c) Microsoft. All rights reserved.
 export interface AppState {
     alerts?: Alerts;
-    unclaimed?: boolean;
-    documentId?: string;
 }
 
 export type Alert = {

samples/apps/copilot-chat-app/webapp/src/redux/features/app/appSlice.ts

@@ -1,9 +1,18 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 import { createSlice, PayloadAction } from '@reduxjs/toolkit';
+import { AlertType } from '../../../libs/models/AlertType';
 import { Alert, Alerts, AppState } from './AppState';
 
-const initialState: AppState = {};
+const initialState: AppState = {
+    alerts: {
+        '0': {
+            message:
+                'SK Copilot is designed for internal use only. By using this chat bot, you agree to not to share confidential or customer information or store sensitive information in chat history. Further, you agree that SK Copilot can collect and retain your chat history for service improvement.',
+            type: AlertType.Info,
+        },
+    },
+};
 
 export const appSlice = createSlice({
     name: 'app',