breaking change: `equals` removed in v2.0.6

**Describe the bug**
The public `equals` function was removed from `equatable_utils.dart` in v2.0.6 causing dependent code to break.

**Additional context**
In my case, I use the [dart-dio OpenAPI generator](https://openapi-generator.tech/docs/generators/dart-dio/) with `equalityCheckMethod: equatable` which broke in v2.0.6.