[board] Clean up some stray muts and imports in the bishop move generator module

board/src/move_generator/bishop.rs

@@ -16,7 +16,6 @@ impl<'pos> MoveGeneratorInternal for ClassicalMoveGenerator<'pos> {
 
     fn move_set_for_piece(position: &Position, placed_piece: PlacedPiece) -> MoveSet {
         let piece = placed_piece.piece();
-        let color = piece.color();
         let square = placed_piece.square();
 
         let blockers = position.occupied_squares();
@@ -61,13 +60,7 @@ impl<'pos> MoveGeneratorInternal for ClassicalMoveGenerator<'pos> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::{
-        piece,
-        piece::{Color, Piece},
-        position,
-        position::DiagramFormatter,
-        BitBoard, Position, Square,
-    };
+    use crate::{piece, piece::Color, position, position::DiagramFormatter, BitBoard};
 
     #[test]
     fn classical_single_bishop_bitboard() {
@@ -108,7 +101,7 @@ mod tests {
     /// Test that a rook can move up to, and then capture, an enemy piece.
     #[test]
     fn classical_single_bishop_with_opposing_color_blocker_bitboard() {
-        let mut pos = position![
+        let pos = position![
             White Bishop on A1,
             Black Knight on C3,
         ];
@@ -125,7 +118,7 @@ mod tests {
 
     #[test]
     fn classical_single_bishop_in_center() {
-        let mut pos = position![
+        let pos = position![
             White Bishop on E4,
         ];