refactor: 移除多边形到边界框的转换逻辑，简化IOU计算过程

ocr_tools/universal_doc_parser/core/layout_utils.py

@@ -489,14 +489,12 @@ class SpanMatcher:
                 continue
             
             bbox1 = span1.get('bbox', [0, 0, 0, 0])
-            bbox1 = CoordinateUtils.poly_to_bbox(bbox1)
             
             for j in range(i + 1, len(spans)):
                 if j in removed:
                     continue
                 
                 bbox2 = spans[j].get('bbox', [0, 0, 0, 0])
-                bbox2 = CoordinateUtils.poly_to_bbox(bbox2)
                 
                 iou = CoordinateUtils.calculate_iou(bbox1, bbox2)