[xc-admin] Fix frontend Dockerfile (#873)

governance/xc_admin/packages/xc_admin_frontend/Dockerfile

@@ -7,6 +7,7 @@ WORKDIR /home/node/
 USER 1000
 
 COPY --chown=1000:1000 governance/xc_admin governance/xc_admin
+COPY --chown=1000:1000 pythnet/message_buffer pythnet/message_buffer
 
 ENV NODE_ENV production
 ENV NEXT_TELEMETRY_DISABLED 1