Fix an issue causing Az.psm1 not to generate

[isra-fel]

Description

Triggered a sign job to verify the fix https://dev.azure.com/azure-sdk/internal/_build/results?buildId=485521&view=results

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

[adxsdkps]

Can one of the admins verify this patch?

[isra-fel]

Root cause: .psm1 has its own scope. If these variables were defined in a .psm1 file, we cannot access them here, so Update-Netcore (line 52) was skipped.