Docker: fix exposed port to be 8071.

I don't 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

Author: tasn

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