[config] Fix libra-config -r default
[config] Fix libra-config -r default

"Validator" is not valid.
Closes: #1205
Approved by: bmwill

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