Add note for no update possible

[FabienTschanz]

Pull Request (PR) description

This PR adds a note to the documentation of the IntuneDeviceEnrollmentPlatformRestriction resource, stating that updating the configuration is no longer possible after deploying it once. This is a restriction by the Microsoft Graph API.

@NikCharlebois I guess the Set and Test method need to be updated. What should they do in the case of an Update or drift detection?

This Pull Request (PR) fixes the following issues

• Fixes [IntuneDeviceEnrollmentPlatformRestriction] Tenant is not Global Admin or Intune Service Admin. Operation is restricted. #5127

Task list

• Added an entry to the change log under the Unreleased section of the file CHANGELOG.md.
  Entry should say what was changed and how that affects users (if applicable), and
  reference the issue being resolved (if applicable).
• Resource parameter descriptions added/updated in the schema.mof.
• Resource documentation added/updated in README.md.
• Resource settings.json file contains all required permissions.
• Examples appropriately added/updated.
• Unit tests added/updated.
• New/changed code adheres to DSC Community Style Guidelines.