fixes invalid rule from hyphen (#11484)
## Summary
When using `add_rule.py`, it produces the following line in `codes.rs`
```
(Flake8Async, "102") => (RuleGroup::Stable, rules::flake8-async::rules::BlockingOsCallInAsyncFunction),
```
Causing a syntax error.
This PR resolves that issue so that the script can be used again.
## Test Plan
Tested manually in new rule creation
