Update optional-claims-reference.md to mention the optional value on idtype

[jmprieur]

@SHERMANOUKO this will also need to be propagated to 1P, ?What is your preference? shall I do another PR?

[prmerger-automator]

@jmprieur : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[prmerger-automator]

@jmprieur : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit e7613df:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/identity-platform/optional-claims-reference.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[learn-build-service-prod]

Learn Build status updates of commit 36b7f5a:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/identity-platform/optional-claims-reference.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[jmprieur]

#sign-off

[prmerger-automator]

Invalid command: '#sign-off'. Only the assigned author of one or more file in this PR can sign off. @cilwerner

[Court72]

Hi @jmprieur - This pull request was opened in the public repo. PMs should work in the private repo, per the Microsoft Docs contributor guide. Would you make this content update in the private repo instead? Thank you! We'll close this PR.

[cilwerner]

@jmprieur, I've fixed this!