onnxruntime

DML EP Mark ImageScalar Test As 'won't fix' (#15894)

ImageScalar is an experimental operator added in ONNX 1.2.1 and removed
in ONNX 1.5 so it's no longer in use.

Changing the comment to won't fix.

---------

Co-authored-by: Dwayne Robinson <dwayner@microsoft.com>