Expose generalized_box_iou to docs (#5302)

* Improve giou loss

* Fix red
Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

docs/source/ops.rst

@@ -21,6 +21,7 @@ Operators
     clip_boxes_to_image
     deform_conv2d
     generalized_box_iou
+    generalized_box_iou_loss
     masks_to_boxes
     nms
     ps_roi_align