[orca-list] Done: Remove the "alternative keybinding" support from Orca

[Joanmarie Diggs <jdiggs igalia com>]

Hey guys.

I just committed to master the change to remove the alternative
keybinding support from Orca. I still need to document how to add
alternative keybindings via orca-customizations.py.

As a related aside, the Orca prefs dialog loads and gets presented much
more quickly now, at least on my machine.

Take care, and thanks again for your input!
--joanie