Fix Windows Powershell encoding test
What does this MR do?
Checks that Windows Powershell outputs the "correct" encoding.
This isn't correct in the same way that Powershell Core is, but that seems to be impossible. This is however better than the encoding output used to be, so will still run this to detect a regression.
Why was this MR needed?
Fixes the Windows Powershell encoding test.
What's the best way to test this MR?
TestPowershellUTF8EncodingStdin should PASS on Windows for both Powershell Core and Windows Powershell.
What are the relevant issue numbers?
Edited by Arran Walker