v1/balance is retired, please use GET /fapi/v2/balance

[Kyrylo]

Describe the bug
Hello, while getting futures account balance, get this error: APIError(code=-5000): GET /fapi/v1/balance is retired, please use GET /fapi/v2/balance

[Dennis Lee]

i also start facing the same error since a day ago

[zweix]

This PR is solving this problem.

[alex]

got the same error