Stop retrying apt packages installation in Docker

The old retries were probably set up to workaround network issues in the
old CI process. We don't need them now.

See 500369f

See #721

Dockerfile

@@ -29,13 +29,10 @@ RUN echo 'deb http://archive.debian.org/debian stretch main\n\
           deb http://archive.debian.org/debian-security stretch/updates main' > /etc/apt/sources.list
 
 # Install package dependencies and add precompiled binary
-RUN for i in {1..5}; do \
-       (apt-get update \
-        && apt-get -y install postgresql-client gdal-bin python-gdal libgdal-java \
-        && break) \
-       || (sleep 5; false); done \
-  && apt-get clean \
-  && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && \
+    apt-get -y install postgresql-client gdal-bin python-gdal libgdal-java && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
 
 # Add scripts
 COPY --from=build /app/scripts/ /app/scripts/