added apt clean after system update to save space

Dockerfile

@@ -12,10 +12,11 @@ COPY export.py /app/export.py
 COPY main.py /app/main.py
 COPY VERSION /app/VERISON
 
-#Make a complete system update
+#Make a complete system update. apt-utils is needed for configuring packages, so we need to install it
 RUN apt update
 RUN apt install apt-utils -y
 RUN apt upgrade -y
+RUN apt clean
 
 #Install pipreqs. This tool is used to make the requirements.txt file automatic. Afterwards install them.
 RUN pip install pipreqs