Updating modified date for 1.15 release notes

Author: VesaJuvonen

docs/spfx/release-1.15.md

@@ -1,7 +1,7 @@
 ---
 title: SharePoint Framework v1.15 preview release notes
 description: Release notes for the SharePoint Framework v1.15 preview release
-ms.date: 3/3/2022
+ms.date: 3/19/2022
 ms.prod: sharepoint
 ms.localizationpriority: high
 ---

docs/toc.yml

@@ -456,7 +456,7 @@
     items:
     - name: Overview
       href: spfx/roadmap.md
-    - name: SPFx v1.15 - March 8, 2022
+    - name: SPFx v1.15 - April 19, 2022
       href: spfx/release-1.15.md      
     - name: SPFx v1.14 - February 17, 2022
       href: spfx/release-1.14.md