nova.py: Remove docs for unused config settings

AFAICT, these settings are not used. I wonder if @mavimo meant to implement these later, but never got around to it?

The other way to go is to implement these settings, but I'm not familiar with these, don't think that my company needs them, and I'm not sure if they require a newer version of python-novaclient or something. In short, I don't feel qualified to implement support, so I'm just removing the docs for the unimplemented feature. Someone else that needs these settings could perhaps add them in at a later date.

BTW, one of settings, `insecure` was misspelled as `insicure` (sic).

Cc: @mavimo, @carsongee (because if this gets merged, #7444 will probably need to be rebased, because it probably touches a lot of the same lines.