[consensus][minor] Minor comment fixes for LedgerInfo
[consensus][minor] Minor comment fixes for LedgerInfo

Closes: #1160
Approved by: dmitri-perelman

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