The test HelpSystem.OnlineHelp.Tests.ps1 needs to be updated after fixing #951 #2465

Two issues about test/powershell/engine/HelpSystem.OnlineHelp.Tests.ps1:

• Some tests don't need to be skipped on Linux and OSX after fixing Investigate updateable help on Linux (Update-Help) #951
• Test data files V2Cmdlets.csv and V3Cmdlets.csv should be put in "assets" folder, not testdata folder. Run dir assets -Recurse under PowerShell\test\powershell for examples. So basically, the folder engine\testdata needs to be renamed to engine\assets.