Update mm-with-cba.md

[sysadm216]

Remove trailing comma from end of sample json file That comma causes agent setup to crash

[learn-build-service-prod]

Learn Build status updates of commit d0bb11a:

✅ Validation status: passed

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migration/mm-with-cba.md	✅Succeeded

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[sysadm216]

Sample JSON is not formatted correctly.
Last line should not end with a comma.

[sysadm216]

#sign-off

[learn-build-service-prod]

Learn Build status updates of commit c02e056:

✅ Validation status: passed

File	Status	Preview URL	Details
migration/mm-with-cba.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