Clarify signal's arguments declaration

Expected type is any sequence. Example presents one-element
tuple and this is only reason why it has comma at the end.

Remove suggest that list need to end with comma
Comma is used only to tell python it's a one-element tuple, not just brackets.

Fixes #177

Author: kam193

source/objects.txt

@@ -82,8 +82,8 @@ The second part, ``None``, indicates the return type of the signal,
 usually ``None``.
 
 ``(int,)`` indicates the signal arguments, here, the signal will only
-take one argument, whose type is int. This argument type list must end with a
-comma.
+take one argument, whose type is int. Types of arguments required by
+signal are declared as a sequence, here it is a one-element tuple.
 
 Signals can be emitted using :meth:`GObject.GObject.emit`:
 
@@ -336,8 +336,8 @@ API
 
         :const:`GObject.SIGNAL_RUN_FIRST` can be replaced with
         :const:`GObject.SIGNAL_RUN_LAST` or :const:`GObject.SIGNAL_RUN_CLEANUP`.
-        ``None`` is the return type of the signal. ``(int,)`` is the list of the
-        parameters of the signal, it must end with a comma.
+        ``None`` is the return type of the signal. ``(int,)`` is the tuple of the
+        parameters of the signal.
 
     .. attribute:: __gproperties__