Appropriate key bindings for closing keybinds help window

[benjiwolff]

The close commands for the keybinds help window are currently hardcoded. When I configure a different key for the Cancel or Close commands, I end up trapped in the help view (if I don't know the default close key).

This change propagates the close bindings to the help window.

[benjiwolff]

Another solution would be to map the :ShowHelp keystroke to the close action. That might be more intuitive since telescope help closes with the same key as it opens ("?").