Remove bishop pin bonus

Shows no regression at LTC after 20K games:

ELO: 0.03 +-2.7 (95%) LOS: 51.0%
Total: 20608 W: 3252 L: 3250 D: 14106

bench: 7516178

src/evaluate.cpp

@@ -163,7 +163,6 @@ namespace {
   #undef S
 
   const Score Tempo            = make_score(24, 11);
-  const Score BishopPin        = make_score(66, 11);
   const Score RookOn7th        = make_score(11, 20);
   const Score QueenOn7th       = make_score( 3,  8);
   const Score RookOnPawn       = make_score(10, 28);
@@ -501,13 +500,6 @@ Value do_evaluate(const Position& pos) {
         if (ei.attackedBy[Them][PAWN] & s)
             score -= ThreatenedByPawn[Piece];
 
-        // Otherwise give a bonus if we are a bishop and can pin a piece or can
-        // give a discovered check through an x-ray attack.
-        else if (    Piece == BISHOP
-                 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
-                 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
-                 score += BishopPin;
-
         // Penalty for bishop with same coloured pawns
         if (Piece == BISHOP)
             score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);