Latest versions of Sphinx (at least 3.1.0) do not need the `*` escaped and
will render the `\` in the output if it is there, so remove it.
Fixes issue #6209.
All concrete network classes are now moved to their own file (eg
network.WLAN.rst) and deconditionalised (remove ..only:: directives). This
makes the network documentation the same for all ports. After this change
there are no more "..only::" directives for different ports, and the only
difference among ports is the very front page of the docs.