[Storage] Remove LibraDBWrapper
[Storage] Remove LibraDBWrapper

Since we are no longer using grpcio, we probably don't the the previous
issue (https://github.com/tikv/grpc-rs/issues/227) any more. So the
wrapper can be removed.

Closes: #2292
Approved by: zamsden

libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core