Remove Debian Jessie updates repository

It was removed from the official mirror, see [1] and links inside for
more information.

[1]: debuerreotype/docker-debian-artifacts#66

debian/jessie/Dockerfile

@@ -10,6 +10,9 @@ ENV DEBIAN_FRONTEND=noninteractive
 # Don't install recommends
 RUN echo 'apt::install-recommends "false";' > /etc/apt/apt.conf.d/00recommends
 
+# Drop EOL repositories
+RUN sed -i '/jessie-updates/d' /etc/apt/sources.list
+
 # Enable extra repositories
 RUN apt-get update && apt-get install -y --force-yes \
     apt-transport-https \