Small cleanups

remove some unneeded assignments, typos, incorrect comments, add authors entry.

closes https://github.com/official-stockfish/Stockfish/pull/4417

no functional change

src/position.cpp

@@ -765,9 +765,6 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
       // Update board and piece lists
       remove_piece(capsq);
 
-      if (type_of(m) == EN_PASSANT)
-          board[capsq] = NO_PIECE;
-
       // Update material hash key and prefetch access to materialTable
       k ^= Zobrist::psq[captured][capsq];
       st->materialKey ^= Zobrist::psq[captured][pieceCount[captured]];