luatelnet: fix grammar

(cherry picked from commit 415dab3b66f17c808045d41577c0b97d7732db33)
Signed-off-by: Pierre Ynard <linkfanel@yahoo.fr>

share/lua/intf/telnet.lua

@@ -183,7 +183,7 @@ while not vlc.misc.should_die() do
     for _, client in pairs(r) do
         local str = client.cmds .. client:recv(1000)
 
-        if not str then -- the telnet client program has leave
+        if not str then -- the telnet client program has left
             client.cmds = "quit"
         elseif string.match(str,"\n") then
             client.cmds = str