Updated SQL documentation example for the new enhancements

[MartinWa]

This PR fixes the code example in the documentation for the changes in #1147

The changes in this PR are as follows:

• Updated example for AD auth set to use the new API

I have read the contributing guidelines and have completed the following:

• [ ] Tested my code end-to-end against a live Azure subscription.
• [x] Updated the documentation in the docs folder for the affected changes.
• [ ] Written unit tests against the modified code that I have made.
• [ ] Updated the release notes with a new entry for this PR.
• [x] Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

If I haven't completed any of the tasks above, I include the reasons why here:

Just documentation changes