Fix #2793: Drop removed functionality from docs

CHANGES/2793.doc

@@ -0,0 +1 @@
+Drop removed functionality about passing ``StreamReader`` as data at client side.

docs/client_quickstart.rst

@@ -320,11 +320,11 @@ As a simple case, simply provide a file-like object for your body::
 Or you can use :class:`aiohttp.streamer` decorator::
 
   @aiohttp.streamer
-  def file_sender(writer, file_name=None):
+  async def file_sender(writer, file_name=None):
       with open(file_name, 'rb') as f:
           chunk = f.read(2**16)
           while chunk:
-              yield from writer.write(chunk)
+              await writer.write(chunk)
               chunk = f.read(2**16)
 
   # Then you can use file_sender as a data provider:
@@ -333,38 +333,6 @@ Or you can use :class:`aiohttp.streamer` decorator::
                           data=file_sender(file_name='huge_file')) as resp:
       print(await resp.text())
 
-Also it is possible to use a :class:`~aiohttp.streams.StreamReader`
-object. Lets say we want to upload a file from another request and
-calculate the file SHA1 hash::
-
-   async def feed_stream(resp, stream):
-       h = hashlib.sha256()
-
-       while True:
-           chunk = await resp.content.readany()
-           if not chunk:
-               break
-           h.update(chunk)
-           stream.feed_data(chunk)
-
-       return h.hexdigest()
-
-   resp = session.get('http://httpbin.org/post')
-   stream = StreamReader()
-   loop.create_task(session.post('http://httpbin.org/post',
-                                 data=stream))
-
-   file_hash = await feed_stream(resp, stream)
-
-
-Because the response content attribute is a
-:class:`~aiohttp.streams.StreamReader`, you can chain get and post
-requests together::
-
-   r = await session.get('http://python.org')
-   await session.post('http://httpbin.org/post',
-                      data=r.content)
-
 
 .. _aiohttp-client-websockets: