fix: import Yolo predictions (detection task with bounding boxes, labels with prediction confidence)

[carbaro]

This pull requests simply accounts for prediction labels produced by yolo's --save_conf option

[niklub]

The change has been already introduced in https://github.com/HumanSignal/label-studio-converter/blob/master/label_studio_converter/imports/yolo.py#L116

[carbaro]

@niklub Thanks for reviewing this PR and letting me know of the alternative PR accepted for this purpose.

I did find that it imports predictions as confirmed detections (as if a user had created and submitted the annotations).

I've created #295 which warns users to use the --out_type if prediction scores are detected while importing with the default value "annotations".