It appears this is an issue introduced in version 2.10.0 of the Az.Sql module. I was able to fix this by setting the
Preferred Azure PowerShell Version field on the Azure DevOps task to 4.6.0. This version of the Az module contains version 2.9.1 of Az.Sql.
Apparently this has been fixed in Azure Powershell v5.3.0, though I have not checked personally.
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