Fix accidentally changed key mappings

[mykola-mokhnach]

I was wondering why https://keycode.info/ returns the keycode for Alt instead of Command if the Cmd key is pressed on Mac keyboard. This change should address this problem.

[stweil]

Thank you. I'll test it soon and then merge your contribution.

[mykola-mokhnach]

@stweil Thanks. Maybe such mapping was done for a reason, because I see LeftCmdKey=Alt_L in RealVNC client options (and only in this one).