pybind/mgr: remove fix (autopep8) rule from tox.ini

pybind/mgr: remove fix (autopep8) rule from tox.ini

Remove the annoying and unloved fix rule from the default envlist of the
pybind/mgr/tox.ini file.

If you don't like this, and want your code formatted automatically, opt
your module into `black` by {format,check}-black rules in tox.ini.
Embrace the much more widely community accepted tool... enjoy the
automatic cookie-cutter formatting... avoid arguing about formatting...
;-)

Signed-off-by: John Mulligan <jmulligan@redhat.com>