[Az.Support] Remove AzPreview.psm1

[grhuangmsft]

Description

Remove unnecessary file AzPreview.psm1 that was merged in this PR: https://github.com/Azure/azure-powershell/pull/24794/files#diff-5335980505af9b2cc1f468b4190795e7fcb410fef5d55f5073ca14ad7ec6cb03

Mandatory Checklist

• Please choose the target release of Azure PowerShell. (⚠️Target release is a different concept from API readiness. Please click below links for details.)

  • [x] General release
  • [ ] Public preview
  • [ ] Private preview
  • [ ] Engineering build
  • [ ] No need for a release

• [x] Check this box to confirm: I have read the Submitting Changes section of CONTRIBUTING.md and reviewed the following information:

• SHOULD update ChangeLog.md file(s) appropriately
  • For SDK-based development mode, update src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md.
    • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header in the past tense.
  • For autorest-based development mode, include the changelog in the PR description.
  • Should not change ChangeLog.md if no new release is required, such as fixing test case only.
• SHOULD regenerate markdown help files if there is cmdlet API change. Instruction
• SHOULD have proper test coverage for changes in pull request.
• SHOULD NOT adjust version of module manually in pull request

[azure-client-tools-bot-prd[bot]]

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