Remove Azure directory v1.0 documentation

What does this MR do and why?

This merge request updates the documentation for integrating Microsoft Azure OAuth 2.0 with GitLab. It removes references to the older Azure Active Directory v1.0 endpoint and instructs users to use the newer v2.0 endpoint instead. The v2.0 endpoint is recommended by Microsoft and uses the Microsoft identity platform.

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Related to #407398 (closed)