[libra_fuzzer] small update to readme
[libra_fuzzer] small update to readme

A friend of mine was playing around with the fuzzer and got confused about this.

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