[Nginx] Remove Dotdeb

> Dotdeb is an extra repository providing up-to-date packages for your 
Debian 8 “Jessie” servers

pica-nginx/Dockerfile

 FROM debian:stretch
 MAINTAINER antoine@barbare.me
 
-RUN echo "deb http://packages.dotdeb.org stretch all" > /etc/apt/sources.list.d/dotdeb.list && \
-wget -O- https://www.dotdeb.org/dotdeb.gpg | apt-key add - && \
-apt-get update -y && apt-get install -y php7.0 php7.0-fpm php7.0-gd php7.0-xml nginx supervisor curl tar
+RUN apt-get update -y && apt-get install -y php7.0 php7.0-fpm php7.0-gd php7.0-xml nginx supervisor curl tar
 
 RUN mkdir -p /run/nginx && \
     mkdir -p /var/www