Fix broken link in microsoft-logins.md client secret section (#36956)

* Initial plan

* Fix incorrect link in microsoft-logins.md

Update the "Create a client secret" link in both moniker ranges to point
to /entra/identity-platform/how-to-add-credentials instead of the old
quickstart-register-app page that no longer exists.

Fixes #34877

Agent-Logs-Url: https://github.com/dotnet/AspNetCore.Docs/sessions/fbd1fab7-dcff-48ab-a6a5-9747bb8fdf3f

Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>

* Apply suggestion from @wadepickett

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>
Co-authored-by: Wade Pickett <wpickett@microsoft.com>

Author: Copilot

aspnetcore/security/authentication/social/microsoft-logins.md

@@ -4,7 +4,7 @@ author: tdykstra
 description: This sample demonstrates the integration of Microsoft account user authentication into an existing ASP.NET Core app.
 ms.author: tdykstra
 ms.custom: mvc
-ms.date: 03/01/2025
+ms.date: 04/07/2026
 monikerRange: '>= aspnetcore-3.1'
 uid: security/authentication/microsoft-logins
 ---
@@ -23,7 +23,7 @@ This sample shows how to enable users to sign in with their work, school, or per
 
 ### Create a client secret
 
-Generate a client secret in the Microsoft Entra admin center by following the steps in [Register an application with the Microsoft identity platform: Add Credentials](/entra/identity-platform/quickstart-register-app?tabs=client-secret#add-credentials).
+Generate a client secret in the Microsoft Entra admin center by following the steps in [Add and manage application credentials in Microsoft Entra ID](/entra/identity-platform/how-to-add-credentials).
 
 ## Store the Microsoft client ID and secret
 
@@ -90,7 +90,7 @@ This sample shows you how to enable users to sign in with their work, school, or
 
 ### Create client secret
 
-Generate a client secret in the Microsoft Entra admin center by following the steps in [Register an application with the Microsoft identity platform: Add Credentials](/entra/identity-platform/quickstart-register-app?tabs=client-secret#add-credentials).
+Generate a client secret in the Microsoft Entra admin center by following the steps in [Add and manage application credentials in Microsoft Entra ID](/entra/identity-platform/how-to-add-credentials).
 
 ## Store the Microsoft client ID and secret