asyncio doc: functions are coroutine, they don't return a coroutine

It's not exact, but easier to understand.

Doc/library/asyncio-protocol.rst

@@ -497,6 +497,6 @@ TCP echo server example, send back received data and close the connection::
 :meth:`Transport.close` can be called immediately after
 :meth:`WriteTransport.write` even if data are not sent yet on the socket: both
 methods are asynchronous. ``yield from`` is not needed because these transport
-methods don't return coroutines.
+methods are not coroutines.
 
 

Doc/library/asyncio-subprocess.rst

@@ -11,13 +11,13 @@ Create a subprocess
    Run the shell command *cmd* given as a string. Return a :class:`~asyncio.subprocess.Process`
    instance.
 
-   This function returns a :ref:`coroutine object <coroutine>`.
+   This function is a :ref:`coroutine <coroutine>`.
 
 .. function:: create_subprocess_exec(\*args, stdin=None, stdout=None, stderr=None, loop=None, limit=None, \*\*kwds)
 
    Create a subprocess. Return a :class:`~asyncio.subprocess.Process` instance.
 
-   This function returns a :ref:`coroutine object <coroutine>`.
+   This function is a :ref:`coroutine <coroutine>`.
 
 Use the :meth:`BaseEventLoop.connect_read_pipe` and
 :meth:`BaseEventLoop.connect_write_pipe` methods to connect pipes.

Doc/library/asyncio-sync.rst

@@ -73,7 +73,7 @@ Lock
       This method blocks until the lock is unlocked, then sets it to locked and
       returns ``True``.
 
-      This method returns a :ref:`coroutine object <coroutine>`.
+      This method is a :ref:`coroutine <coroutine>`.
 
    .. method:: release()