Make Windows Docker tests use pwsh shell
With !2492 (merged), we've added pwsh to the helper image, however until it is merged and that image is available as the latest tag, we can't upgrade getRunnerConfigForOS to use pwsh on Windows tests.
With !2492 (merged), we've added pwsh to the helper image, however until it is merged and that image is available as the latest tag, we can't upgrade getRunnerConfigForOS to use pwsh on Windows tests.