Update .whatsnew.release.json

Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

Author: BillWagner

.whatsnew.release.json

@@ -16,7 +16,7 @@
         "maximumNumberOfArticles": 3,
         "tocParentNode": "What's new",
         "repoTocFolder": "docs/whats-new",
-        "indexParentNode": ".NET Release updates",
+        "indexParentNode": ".NET release updates",
         "repoIndexFolder": "docs/whats-new"
     },
     "areas": [