Stop creating a NodeJS build image

All it does is set some environment variables so just set those on the command-line

client/.dockerignore

@@ -1,2 +0,0 @@
-node_modules
-dist

client/Dockerfile

@@ -1,14 +0,0 @@
-# Changes to this file will not take effect in CI
-# until the image version in the CI config is updated. See
-# https://github.com/weaveworks/scope/blob/master/.circleci/config.yml#L11
-FROM node:10.19
-ENV NPM_CONFIG_LOGLEVEL=warn
-ENV NPM_CONFIG_PROGRESS=false
-ENV XDG_CACHE_HOME=/home/weave/scope/.cache
-
-ARG revision
-LABEL maintainer="Weaveworks <help@weave.works>" \
-      org.opencontainers.image.title="scope-ui-build" \
-      org.opencontainers.image.source="https://github.com/weaveworks/scope" \
-      org.opencontainers.image.revision="${revision}" \
-      org.opencontainers.image.vendor="Weaveworks"