Bump to node20 in Dockerfile.

Author: na9da

deploy/docker/Dockerfile

@@ -1,5 +1,5 @@
 # Docker image for the primary terria map application server
-FROM node:16
+FROM node:20
 
 RUN mkdir -p /usr/src/app && mkdir -p /etc/config/client
 WORKDIR /usr/src/app/component