update frontmatter

- update timestamp date to indicate last updated date doc changed... @Steven-Jia please include this in future updates
- remove `ms.prod` metadata from frontmatter - set globally in this section in the **docfx.json** file

Author: andrewconnell

docs/business-apps/power-apps/get-started/create-your-first-custom-form.md

@@ -1,8 +1,7 @@
 ---
 title: Customize a form for a SharePoint list
 description: Customize a form for a SharePoint list
-ms.date: 05/18/2021
-ms.prod: sharepoint
+ms.date: 09/27/2022
 ms.localizationpriority: high
 ---