update Tor Browser proposal 102 to account for Tails team feedback

We need to update proposal 102 "Integration of Tor Launcher into Tor Browser Core" to account for feedback we received from the Tails team (intrigeri). See the discussion here: https://lists.torproject.org/pipermail/tbb-dev/2019-February/000962.html https://lists.torproject.org/pipermail/tbb-dev/2019-February/000963.html https://lists.torproject.org/pipermail/tbb-dev/2019-February/000964.html