message: Update comments for MAX_LENGTH consts
  MAX_LENGTH_DB_KEY is used in both db_read and db_write
  `Max value` instead of `Max key` in MAX_LENGTH_DB_VALUE doc comment
diff: @@ -30,9 +30,9 @@ use crate::GasInfo;
  const KI: usize = 1024;
  /// A mibi (mega binary)
  const MI: usize = 1024 * 1024;
  -/// Max key length for db_write (i.e. when VM reads from Wasm memory)
  +/// Max key length for db_write/db_read (i.e. when VM reads from or writes to Wasm memory)
  const MAX_LENGTH_DB_KEY: usize = 64 * KI;
  -/// Max key length for db_write (i.e. when VM reads from Wasm memory)
  +/// Max value length for db_write (i.e. when VM reads from Wasm memory)
  const MAX_LENGTH_DB_VALUE: usize = 128 * KI;
  /// Typically 20 (Cosmos SDK, Ethereum), 32 (Nano, Substrate) or 54 (MockApi)
  const MAX_LENGTH_CANONICAL_ADDRESS: usize = 64;
  