Update Dockerfile

Dockerfile

@@ -8,7 +8,7 @@ WORKDIR /app
 COPY . /app
 
 # 安装依赖
-RUN apt update & apt install software-properties-common & add-apt-repository "deb http://archive.debian.org/debian jessie-backports main" & apt update & apt install ffmpeg
+RUN apt-get update && apt-get install ffmpeg
 RUN pip install --no-cache-dir gunicorn
 RUN pip install --no-cache-dir -r requirements.txt
 RUN pip install --no-cache-dir flask