Fix docs build
Sphinx 3.0.1 complains with:
horizon/horizon/base.py:docstring of horizon.Panel:33:duplicate object
description of horizon.Panel.nav, other instance in contributor/ref/horizon,
use :noindex: for one of them
Fix the two problem.
@@ -273,7 +273,6 @@ class Panel(HorizonComponent):
Default: ``None``.
.. attribute:: nav
- .. method:: nav(context)
The ``nav`` attribute can be either a boolean value or a callable
which accepts a ``RequestContext`` object as a single argument
@@ -453,7 +452,6 @@ class Dashboard(Registry, HorizonComponent):
which are not connected to specific panels. Default: ``None``.
.. attribute:: nav
- .. method:: nav(context)
The ``nav`` attribute can be either a boolean value or a callable
which accepts a ``RequestContext`` object as a single argument
