Don't test with aiohttp 3.6 and older on Python 3.10

aiohttp 3.6 and older use Python features which were removed in Python
3.10:

                assert port is not None
    >           hosts = await asyncio.shield(self._resolve_host(
                    host,
                    port,
                    traces=traces), loop=self._loop)
    E               TypeError: shield() got an unexpected keyword argument 'loop'

    .tox/py3.10-aiohttp35/lib/python3.10/site-packages/aiohttp/connector.py:952: TypeError

To avoid test failures, we remove unsupported combinations from GitHub
workflows.

.github/workflows/ci.yml

@@ -54,10 +54,6 @@ jobs:
           - python-version: 3.9
             aiohttp-version: aiohttp38
 
-          - python-version: "3.10"
-            aiohttp-version: aiohttp35
-          - python-version: "3.10"
-            aiohttp-version: aiohttp36
           - python-version: "3.10"
             aiohttp-version: aiohttp37
           - python-version: "3.10"