chore: remove unnecessary arguments

[is2ei]

This PR removes unnecessary arguments and improves test coverage.

In #40, a workaround is added to avoid the undefined error.
It says "In some cases" but it is actually "In all cases" because the arguments are changed in v7.
Ref: ajv-validator/ajv@9e2e6b9#diff-489d67aa91e09063da5c34330526703a13b3cdedf7d86426173d0bc62183b6c7L36-L50

Now there are 2 arguments data and dataCxt.
Ref: https://github.com/ajv-validator/ajv/blob/master/lib/types/index.ts#L50-L57
Ref2: https://github.com/ajv-validator/ajv/blob/master/lib/vocabularies/code.ts#L75-L91

Therefore, I guess we can remove the if statement.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm