Remove some dead code in notification:reset_timeout()

This code is inside an "if new_timeout and [something else]". Thus, it
only executes when new_timeout is "truthy". Thus, "new_timeout or
[whatever]" will always evaluate to "new_timeout".

This commit removes that tiny bit of dead code.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/naughty/notification.lua

@@ -467,7 +467,7 @@ function notification:reset_timeout(new_timeout)
     -- Do not set `self.timeout` to `self.timeout` since that would create the
     -- timer before the constructor ends.
     if new_timeout and self.timer then
-        self.timeout = new_timeout or self.timeout
+        self.timeout = new_timeout
     end
 
     if self.timer and not self.timer.started then