Update dockerfile

Author: hadikoub

docker/dockerfile

@@ -29,6 +29,7 @@ RUN pip install -r requirements.txt
 
 
 WORKDIR ${HOME}
+#Checkout version should be 4.4.0 when the new version is released 
 RUN git clone http://github.com/opencv/opencv.git && cd opencv \
     && git checkout 992c908b566d264b824680d0cf7d668cdf918254    \
     && mkdir build && cd build              \