Investigate codecov on `lotus_json` actors

[LesnyRumcajs]

Summary

See https://app.codecov.io/github/ChainSafe/forest/tree/main/src%2Flotus_json%2Factors, there are some snapshot tests that are not covered/run. To be investigated.

Completion Criteria

• [ ]

Additional Links & Resources

[hanabi1224]

Closing as we now have 88% code coverage on lotus_json directory.

https://app.codecov.io/github/ChainSafe/forest/tree/main/src