[refactor] Remove the IEthAPI interface from rpcapi/api_eth.go since it's largely unused and the expected API methods are tested in "TestExpectedMethods" in eth_api_test.go.

[Unique-Divine]

eth/rpc/rpcapi/api_eth.go:21 - TODO: Remove this interface over since it's largely unused and the expected
- Action: Remove unused interface
- Impact: Code cleanup