Docker: fix exposed port to be 8071. (#1596)

I don't think exposing 8080 ever did anything as the server is listening
on 8071. It looks like a customer has been facing issues with their
docker setup not letting them map the port because it doesn't match the
exposed from the dockerfile. I'm not sure how it works for everyone else
but not here though anyhow it should be fixed.

Ref: https://x.com/0xblacklight/status/1872430388158533871

server/Dockerfile

@@ -50,7 +50,7 @@ RUN apt-get update && apt-get install -y \
         rm -rf /var/lib/apt/lists/*
 
 USER appuser
-EXPOSE 8080
+EXPOSE 8071
 
 COPY --from=build /app/target/release/svix-server /usr/local/bin/svix-server