Fix use of registry in nightly tests causing failure on Linux - #3377

This if((-not ($skipTest)) -and $IsWindows) block was introduced because our default-browser-discovery code, which was used in Get-Help -Online, doesn't work correctly on the Azure code-coverage VM (see PR #3051). After #3281, that code was repalced by calling into ShellExecuteEx. Although I never tried on the Azure code-coverage VM, I think the problem should be solved, and if that's the case, this if block can be removed completely.

LGTM, I'm going to re-assign it to Dongbo. If he is right that we don't need this code, it would be better to remove it completely.

Dongbo Wang (@daxian-dbw) since this is blocking nightly's from passing, we should make a call on this sooner than later. perhaps we should merge this to get it passing and separately see if the code is still needed for CC?

Steve Lee (@SteveL-MSFT) that sounds reasonable. #3079 is tracking this issue.