[board] Build error and warning fixes

- Remove unused import from bit_scanner.rs
- Rename PieceShape → Shape in the Position tests

board/src/position.rs

@@ -96,12 +96,13 @@ impl fmt::Display for Position {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::piece::Shape;
 
     #[test]
     fn place_piece_at() {
         let mut position = Position::empty();
 
-        let piece = Piece::new(Color::White, PieceShape::Queen);
+        let piece = Piece::new(Color::White, Shape::Queen);
         let square = Square::from_algebraic_string("e4").expect("Unable to get e4 square");
 
         position