Updated pipeline files to support change of master to main

[johlju]

Pull Request (PR) description

• ActiveDirectoryDsc
  • Renamed master branch to main (issue #641).

This Pull Request (PR) fixes the following issues

• Fixes #641

Task list

• [x] Added an entry to the change log under the Unreleased section of the file CHANGELOG.md. Entry should say what was changed and how that affects users (if applicable), and reference the issue being resolved (if applicable).
• [ ] Resource documentation added/updated in README.md.
• [ ] Resource parameter descriptions added/updated in README.md, schema.mof and comment-based help.
• [ ] Comment-based help added/updated.
• [ ] Localization strings added/updated in all localization files as appropriate.
• [x] Examples appropriately added/updated.
• [ ] Unit tests added/updated. See DSC Community Testing Guidelines.
• [ ] Integration tests added/updated (where possible). See DSC Community Testing Guidelines.
• [x] New/changed code adheres to DSC Community Style Guidelines.

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This change is 

[johlju]

@X-Guardian this is the PR for step 8 in this guide https://dsccommunity.org/blog/convert-master-to-main/. The tests wont pass in this PR until the all steps have been completed. Do you have time to do a quick review on this? Then I continue with the rest of the steps.

[johlju]

FYI The tests will pass in my fork where the rename has been made https://dev.azure.com/viscalyx/ActiveDirectoryDsc/_build/results?buildId=1385&view=results