Add deprecation notice on Batch cmdlet

[matthchr]

Description

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate ChangeLog.md file(s) has been updated:
  • For any service, the ChangeLog.md file can be found at src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md
  • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header -- no new version header should be added
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • a cmdlet design review was approved for the changes in this repository (Microsoft internal only)
  • the markdown help files have been regenerated using the commands listed here

The upcoming breaking change has already been signed off and merged in #10001

[erich-wang]

@matthchr , please update ChangeLog.md for your service,
src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md

[markcowl]

@matthchr this will be ready to merge once you add a changelog update

[matthchr]

Updated Changelog

All review comments addressed