update timestamp in frontmatter to reflect change

Author: andrewconnell

docs/spfx/web-parts/basics/integrate-with-property-pane.md

@@ -1,7 +1,7 @@
 ---
 title: Make your SharePoint client-side web part configurable
 description: Configure custom properties in your web part by using the property pane.
-ms.date: 06/22/2020
+ms.date: 04/06/2020
 ms.prod: sharepoint
 ms.localizationpriority: high
 ---