Fix malformed redirection.json — restore app-background-task redirect

Copilot's applied suggestion accidentally merged two JSON objects together,
clobbering the existing app-background-task redirect. Splits the three
entries back into separate, valid objects.

Co-authored-by: Copilot <[email protected]>

Author: GrantMeStrength

.openpublishing.redirection.json

@@ -11533,6 +11533,9 @@
     {
       "source_path": "hub/apps/windows-app-sdk/applifecycle/app-background-task.md",
       "redirect_url": "/windows/apps/windows-app-sdk/applifecycle/background-tasks",
+      "redirect_document_id": false
+    },
+    {
       "source_path": "hub/apps/desktop/modernize/desktop-to-uwp-distribute.md",
       "redirect_url": "/windows/msix/desktop/source-code-overview",
       "redirect_document_id": false