Remove test workaround once PowerShell has Alpine support for Arm

[mthalman]

The changes in https://github.com/dotnet/dotnet-docker/pull/2543 included a change to disable a test due to PowerShell not being available in the image because of its lack of support for Arm on Alpine (https://github.com/PowerShell/PowerShell/issues/14667, https://github.com/PowerShell/PowerShell/issues/12937). Once PowerShell does provide support and it is incorporated into the sdk images, the test workaround should be removed.

https://github.com/dotnet/dotnet-docker/blob/426ed5f048c16cd675b72c30263e45be392215c3/tests/Microsoft.DotNet.Docker.Tests/SdkImageTests.cs#L168-L172

[lbussell]

This will be addressed by https://github.com/dotnet/dotnet-docker/pull/4926 (not by installing PowerShell on arm Alpine images)