Update Dockerfile

Dockerfile

@@ -26,7 +26,7 @@ RUN pip install -r requirements.txt
 
 RUN mkdir examples && \
     cd examples && \
-    for i in $(seq 1 12); do wget "https://raw.githubusercontent.com/memory-overflow/standard-ellipse-detection/master/images/test$i.jpg?raw=true"; done && \
+    for i in `seq 1 12`; do wget "https://raw.githubusercontent.com/memory-overflow/standard-ellipse-detection/master/images/test$i.jpg?raw=true"; done && \
     image_files=("13.jpg" "27.jpg" "35.jpg" "43.jpg" "666.jpg" "666_negative.jpg" "666_positive.jpg" "different-polarity-detection_all.jpg" "im9933.jpg") && \
     for file in "${image_files[@]}"; do wget "https://github.com/AlanLuSun/High-quality-ellipse-detection/blob/master/pics/$file?raw=true"; done