fix server/client mixup in client docstrings (#312)

Author: Sasja

src/engineio/asyncio_client.py

@@ -135,9 +135,9 @@ async def wait(self):
             await self.read_loop_task
 
     async def send(self, data):
-        """Send a message to a client.
+        """Send a message to the server.
 
-        :param data: The data to send to the client. Data can be of type
+        :param data: The data to send to the server. Data can be of type
                      ``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
                      or ``dict``, the data will be serialized as JSON.
 

src/engineio/client.py

@@ -201,9 +201,9 @@ def wait(self):
             self.read_loop_task.join()
 
     def send(self, data):
-        """Send a message to a client.
+        """Send a message to the server.
 
-        :param data: The data to send to the client. Data can be of type
+        :param data: The data to send to the server. Data can be of type
                      ``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
                      or ``dict``, the data will be serialized as JSON.
         """