Update Docs for ConPTY support

[colemickens]

https://github.com/PowerShell/Win32-OpenSSH/wiki/TTY-PTY-support-in-Windows-OpenSSH

Can this page be updated to discuss the new TTY situation nwo that ConPTY is supported?

[mgkuhn]

The line “Windows OS does not have inbuilt support for a pseudoterminal.” clearly needs to be changed to “Windows versions before Windows 10 1809 did not have built-in support for a pseudoterminal. On more recent versions, OpenSSH 7.9 or newer can connect stdin/stdout of a command-line applications similar to how it does on POSIX systems.”
Anything else?

[bagajjal]

@colemickens , @mgkuhn - Thank you. I updated the wiki