Remove PowerShell 6 placeholders on Azure

When a sufficient number of PowerShell 6 apps migrate to PowerShell 7, update the default placeholder pool configuration in Antares to remove PowerShell 6 placeholders in order to save these resources.

Start by locating Antares' default placeholder pool configuration and confirm how the migration threshold for PowerShell 6 apps is determined. Once a sufficient number of apps have migrated to PowerShell 7, remove the PowerShell 6 placeholders and verify that the configuration no longer allocates those resources.

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