Remove redundant reactions in Sudoku
Remove redundant reactions in Sudoku

* Remove validate reaction for when-done validation

  This will make it easier to port to reaction-less, as there will be one
  less reaction to make a fallback for.

  This also makes the game simpler to play, since checking if the board is
  done should be done when the user "finishes", rather than having to
  explicitly.

* Make help a kill-able dropdown

  Like Minesweeper, this will make the help page send a message rather
  than edit it. It will also close if another reaction was pressed or if
  a space was selected.

Because of this, we don't need the resume button anymore.

Ikusaba-san/Chiaki-Nanami