Bug 2139: OSM OCI images have 172.21.1.1 as apt proxy

Removes the apt proxy configuration from the final
image layers

Change-Id: I3f2dfd81a04b42d3ee570cdc71ca41da39e621d0
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/docker/NG-UI/Dockerfile b/docker/NG-UI/Dockerfile
index c4d67df..74aa1d4 100644
--- a/docker/NG-UI/Dockerfile
+++ b/docker/NG-UI/Dockerfile
@@ -62,6 +62,8 @@
     nginx=1.18.* && \
     rm -rf /var/lib/apt/lists/*
 
+RUN rm -f /etc/apt/apt.conf.d/proxy.conf
+
 # Removing the Nginx default page.
 RUN rm -rf /usr/share/nginx/html/*