There is no need for setting the availability of desktop sharing anymore. It can
now be detected on the spot.
The reson for the previous code was that way back when browser extensions were
needed, it was possible to start a conference without desktopo sharing support
and get it afterwards. This is no longer the case.
If toggle SS is executed too early and lib-jitsi-meet is not yet
initialized toggle SS will fail. Now we are storing the whether
SS is on or off and when lib-jitsi-meet is ready we are starting
SS if needed.