Wrong signature for `KafkaError`'s 1st parameter in `.pyi`

The name of the 1st parameter for `KafkaError`'s initialiser in `src/confluent_kafka/cimpl.pyi` is now `code` (ref [here](https://github.com/confluentinc/confluent-kafka-python/blob/7d0abd551c5061e655fbf403f9baa09af040e29b/src/confluent_kafka/cimpl.pyi#L229-L230)), however this does not match the underlying code itself.

For example, if we try to create an instance of `KafkaError` according to the signature:

```python
# kafka_error_test.py

from confluent_kafka import KafkaError

error = KafkaError(code=1)
```

Then `mypy` is OK with this

```
# mypy kafka_error_test.py
Success: no issues found in 1 source file
```

But we get a `TypeError` when it runs

```
# python kafka_error_test.py
Traceback (most recent call last):
File "/workspaces/kafka_error_test.py", line 5, in
error = KafkaError(code=1)
```

I'm happy to submit a PR to fix this but which way do we want to go here? Change the signature in the `.pyi` file so it matches what [the underlying C code expects](https://github.com/confluentinc/confluent-kafka-python/blob/7d0abd551c5061e655fbf403f9baa09af040e29b/src/confluent_kafka/src/confluent_kafka.c#L310-L313)? Or change the underlying C code to match up with the signature?