Bump opencv-python from 4.2.0.32 to 4.8.1.78 in /demos/instance_occlsegm

Bumps [opencv-python](https://github.com/opencv/opencv-python) from 4.2.0.32 to 4.8.1.78.
- [Release notes](https://github.com/opencv/opencv-python/releases)
- [Commits](https://github.com/opencv/opencv-python/commits)

---
updated-dependencies:
- dependency-name: opencv-python
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

demos/instance_occlsegm/requirements.txt

@@ -13,7 +13,7 @@ imgaug>=0.2.7
 labelme>=2.9,<5.0.0
 matplotlib
 numpy
-opencv-python==4.2.0.32
+opencv-python==4.8.1.78
 pathlib2
 Pillow
 protobuf==3.17.3