[Az.ContainerRegistry] fix parameter type for update-azcontainerregistryrepository

[VeryEarly]

Description

$false was passed when optional parameter was not provided for type bool, change to bool? which reflect desired behavior.

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)
    • {Please put the link here}
  • the markdown help files have been regenerated using the commands listed here

[BethanyZhou]

No idea why this breaking change was not detected, it causes other PR's CI failed. Could you have a look? @wyunchi-ms @VeryEarly

[isra-fel]

Given that the breaking changes were not detected, and the CI ran suspeciously fast (azure-powershell - powershell-core
succeeded on 26 Apr in 17m 28s), I guess it was caused by the throtling of GitHub API, causing CI unable to get the list of changed files, so some of the steps were skipped.