asyncio.exceptions.CancelledError

**Describe the bug**
A clear and concise description of what the bug is.

```
Traceback (most recent call last):
File "venv/lib/python3.9/site-packages/aiokafka/util.py", line 41, in wait_for
return await fut
asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "venv/lib/python3.9/site-packages/aiokafka/client.py", line 505, in send
result = await future
File "venv/lib/python3.9/site-packages/aiokafka/util.py", line 41, in wait_for
return await fut
File "venv/lib/python3.9/site-packages/async_timeout/__init__.py", line 129, in __aexit__
self._do_exit(exc_type)
File "venv/lib/python3.9/site-packages/async_timeout/__init__.py", line 212, in _do_exit
raise asyncio.TimeoutError
asyncio.exceptions.TimeoutError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "venv/lib/python3.9/site-packages/aiokafka/consumer/fetcher.py", line 660, in _proc_fetch_request
response = await self._client.send(node_id, request)
File "venv/lib/python3.9/site-packages/aiokafka/client.py", line 510, in send
raise RequestTimedOutError()
aiokafka.errors.RequestTimedOutError: [Error 7] RequestTimedOutError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "venv/lib/python3.9/site-packages/aiokafka/consumer/fetcher.py", line 663, in _proc_fetch_request
await asyncio.sleep(self._retry_backoff)
File "/usr/lib/python3.9/asyncio/tasks.py", line 652, in sleep
return await future
asyncio.exceptions.CancelledError

```

I'm wondering if we can ignore this type of exceptions https://github.com/aio-libs/aiokafka/blob/master/aiokafka/consumer/fetcher.py#L458 as the treatment here https://github.com/aio-libs/aiokafka/blob/master/aiokafka/consumer/fetcher.py#L450

**Environment (please complete the following information):**
- aiokafka version (`python -c "import aiokafka; print(aiokafka.__version__)"`): 0.10.0