update Dockerfile

Dockerfile

 FROM debian:stable-slim
 MAINTAINER Drone CI/CD
 
-
 RUN echo $'\n\
       Acquire::http  { Proxy "'$HTTP_PROXY$'"; } \n\
       Acquire::https { Proxy "https://"; }; \n\
-    >> /etc/apt/apt.conf.d/01-proxy
-
-
+'   >> /etc/apt/apt.conf.d/01-proxy
 
 RUN apt-get update && \
     apt-get --yes upgrade && \