How to remove title bar in awesome window manager ver >4

In your rc.lua file, look for

-- Add title bars to normal clients and dialogs
{ rule_any = {type = { "normal", "dialog" }
  }, properties = { titlebars_enabled = true }
},

and change

titlebars_enabled = true

to

titlebars_enabled = false

A bit late for this (1 year ago !)...
I replace as said previously by Emmanuel in the rules section. But when I made titlebars appear they were empty, no icons, no textbox... nothing.
My workaround was to leave titlebars_enabled = true in the rules section.
and in the signals section (in the "manage" handle) : add the titlebar and hide it (the 2 last lines in the code below) when I start awesome. When I toggle its display, the titlebar appears with icons and texts :

-- Signal function to execute when a new client appears.
client.connect_signal("manage", function (c)
  -- Set the windows at the slave,
  -- i.e. put it at the end of others instead of setting it master.
  -- if not awesome.startup then awful.client.setslave(c) end

 if awesome.startup and
  not c.size_hints.user_position
  and not c.size_hints.program_position then
    -- Prevent clients from being unreachable after screen count changes.
    awful.placement.no_offscreen(c)
 end
--
 awful.titlebar(c,{size=10})
 awful.titlebar.hide(c)
end)