Fix: Some typos found using codespell

src/void_cmd.cpp

@@ -28,7 +28,7 @@ static void DrawTile_Void(TileInfo *ti)
 
 static int GetSlopePixelZ_Void(TileIndex tile, uint x, uint y)
 {
-	/* This function may be called on tiles outside the map, don't asssume
+	/* This function may be called on tiles outside the map, don't assume
 	 * that 'tile' is a valid tile index. See GetSlopePixelZOutsideMap. */
 	int z;
 	Slope tileh = GetTilePixelSlopeOutsideMap(x >> 4, y >> 4, &z);