[msid] bump date for optional claims article

Token config went GA, the article was updated as such in https://github.com/MicrosoftDocs/azure-docs-pr/pull/112347, but I forgot to bump the date. This corrects that oversight.
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cc: @rwike77

Author: mmacy

articles/active-directory/develop/active-directory-optional-claims.md

@@ -9,7 +9,7 @@ ms.service: active-directory
 ms.subservice: develop
 ms.topic: conceptual
 ms.workload: identity
-ms.date: 3/11/2020
+ms.date: 04/22/2020
 ms.author: ryanwi
 ms.reviewer: paulgarn, hirsin, keyam
 ms.custom: aaddev