fix #1: invalid knight moves bitboard for A3 square

Author: dechristopher

engine.go

@@ -380,7 +380,7 @@ var (
 4122, // B2
 32901, // C2
 16450, // D2
-16946, // A3
+16898, // A3
 41217, // B3
 22536, // C3
 9220, // D3

move_test.go

@@ -21,10 +21,10 @@ type perfTest struct {
 // https://www.chessprogramming.org/Perft_Results
 var perfResults = []perfTest{
 {pos: unsafeOFEN("ppkn/4/4/NKPP w NCFncf - 0 1"), nodesPerDepth: []int{
-10, 84, 642, 4373, 29389, 185151,
+10, 84, 642, 4375, 29309, 183931,
 }},
 {pos: unsafeOFEN("ppkn/4/2P1/NK1P w NCFncf - 0 1"), nodesPerDepth: []int{
-10, 75, 538, 3432,
+10, 75, 538, 3433,
 }},
 }