Set C# language version to preview/9.0 (#13090)
Set C# language version to preview/9.0 (#13090)


daxian-dbw/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,TravisEz13/PowerShell,PaulHigin/PowerShell,TravisEz13/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,daxian-dbw/PowerShell,PaulHigin/PowerShell,JamesWTruher/PowerShell-1,daxian-dbw/PowerShell,PaulHigin/PowerShell,JamesWTruher/PowerShell-1