message: Clarify `tick` logic in `game_of_life`
diff: @@ -200,14 +200,12 @@ mod grid {
  let is_populated = self.alive_cells.contains(&(i, j));
  match amount {
  - 2 if is_populated => {}
  + 2 | 3 if is_populated => {}
  3 => {
  - if !is_populated {
  - self.alive_cells.insert((i, j));
  - }
  + let _ = self.alive_cells.insert((i, j));
  }
  _ if is_populated => {
  - self.alive_cells.remove(&(i, j));
  + let _ = self.alive_cells.remove(&(i, j));
  }
  _ => {}
  }
  