update frontmatter timestamp to reflect doc change date

Author: andrewconnell

docs/spfx/extensions/get-started/serving-your-extension-from-sharepoint.md

@@ -1,7 +1,7 @@
 ---
 title: Deploy your extension to SharePoint (Hello World part 3)
 description: Deploy your SharePoint Framework Application Customizer to SharePoint and see it working on modern SharePoint pages.
-ms.date: 06/19/2020
+ms.date: 06/07/2022
 ms.prod: sharepoint
 ms.localizationpriority: high
 ms.custom: scenarios:getting-started