remove some unused definitions

I added them at the very start when I wasn't quite sure what I wanted or needed;
at this point they're just not necessary anywhere.

Minesweeper/Moves.agda

@@ -52,18 +52,6 @@ grid [ coords ]↝✓ guess = ∀ grid′ →
   grid′ ✓ →
     guess ⚐✓ lookup coords grid′
 
--- solvable boards: a board is solvable when there is a rule-respecting way to fill its unfilled tiles
-record Solvable {bounds} (unsolved : Board Tile bounds) : Set where
-  field
-    solution  : Board KnownTile bounds
-    relevance : unsolved ↝⊞ solution
-    validity  : solution ✓
-
--- "play" a valid move on a solvable board, giving evidence that it holds in the provided solution
-play : ∀ {bounds grid} (coords : Coords bounds) {guess} →
-  grid [ coords ]↝✓ guess → (solved : Solvable grid) →
-    guess ⚐✓ lookup coords (Solvable.solution solved)
-play coords move solved = move (Solvable.solution solved) (Solvable.relevance solved) (Solvable.validity solved)
 
 
 invert⚐ : Guess → Guess