rubocop: disable Performance/RegexpMatch
rubocop: disable Performance/RegexpMatch

Fixes the following failure:

```
lib/airbrake-ruby/backtrace.rb:160:28:
C: Performance/RegexpMatch: Use match? instead of =~ when MatchData is not used.
            return true if frame =~ Patterns::EXECJS_SIMPLIFIED
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```

It's a new cop. We cannot use its suggestion because we support older
rubies, which don't support the new method.

airbrake/airbrake-ruby,airbrake/airbrake-ruby