Fix capitalization of asyncio and aiohttp (#2516) (#2517)

Author: github-actions[bot]

docs/guide/installation.asciidoc

@@ -22,4 +22,4 @@ $ python -m pip install elasticsearch[async]
 --------------------------------------------
 
 Read more about 
-https://elasticsearch-py.readthedocs.io/en/master/async.html[how to use Asyncio with this project].
+https://elasticsearch-py.readthedocs.io/en/master/async.html[how to use asyncio with this project].

docs/sphinx/async.rst

@@ -1,11 +1,11 @@
-Using Asyncio with Elasticsearch
+Using asyncio with Elasticsearch
 ================================
 
  .. py:module:: elasticsearch
     :no-index:
 
 The ``elasticsearch`` package supports async/await with
-`Asyncio <https://docs.python.org/3/library/asyncio.html>`_ and `Aiohttp <https://docs.aiohttp.org>`_.
+`asyncio <https://docs.python.org/3/library/asyncio.html>`_ and `aiohttp <https://docs.aiohttp.org>`_.
 You can either install ``aiohttp`` directly or use the ``[async]`` extra:
 
  .. code-block:: bash