Fix typo in docstring in `metrics.py` (#15842)

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/utils/metrics.py

@@ -178,7 +178,7 @@ def _get_covariance_matrix(boxes):
         boxes (torch.Tensor): A tensor of shape (N, 5) representing rotated bounding boxes, with xywhr format.
 
     Returns:
-        (torch.Tensor): Covariance metrixs corresponding to original rotated bounding boxes.
+        (torch.Tensor): Covariance matrices corresponding to original rotated bounding boxes.
     """
     # Gaussian bounding boxes, ignore the center points (the first two columns) because they are not needed here.
     gbbs = torch.cat((boxes[:, 2:4].pow(2) / 12, boxes[:, 4:]), dim=-1)