Updated BIB reference to DISFlow paper

modules/optflow/doc/optflow.bib

@@ -38,10 +38,10 @@
   organization={IEEE}
 }
 
-@article{Kroeger2016,
+@inproceedings{Kroeger2016,
+  author={Till Kroeger and Radu Timofte and Dengxin Dai and Luc Van Gool},
   title={Fast Optical Flow using Dense Inverse Search},
-  author={Kroeger, Till and Timofte, Radu and Dai, Dengxin and Van Gool, Luc},
+  booktitle={Proceedings of the European Conference on Computer Vision ({ECCV})},
-  journal={arXiv preprint arXiv:1603.03590},
   year = {2016}
 }