build(deps): bump opencv-python-headless

Bumps [opencv-python-headless](https://github.com/opencv/opencv-python) from 4.7.0.72 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-headless
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

demos/image_classification_example/requirements.txt

@@ -2,6 +2,6 @@ numpy==1.23.5
 grpcio==1.53.2
 tensorflow==2.12.1
 tensorflow-serving-api==2.11.1
-opencv-python-headless==4.7.0.72
+opencv-python-headless==4.8.1.78
 paho-mqtt==1.6.1
 bentoml==1.2.5