message: modifies comment - height upper bound
diff: @@ -329,7 +329,9 @@ where
  pub fn height(&self) -> Height {
  // Height:
  - // - should not exceed std::u64::MAX - 1 to ensure the parent check doesn't
  + // - Reasonable to assume that the height of the block chain will not grow enough to exceed
  + // std::u64::MAX - 1 in the next million years at least
  + // - The upper limit of std::u64::MAX - 1 ensures that the parent check doesn't
  // cause addition overflow.
  // (Block::make_block)
  assumed_postcondition!(self.height < std::u64::MAX);
  