chore(deps): update node:8.16.0 docker digest to 39c16ad

Author: renovate-bot

.circleci/config.yml

@@ -6,7 +6,7 @@ machine:
 jobs:
   build:
     docker:
-      - image: node:8.16.0@sha256:4d7a0358ce961c70514ac6e65a57cbeda3a143faba5da3fec22e62262f6448b0
+      - image: node:8.16.0@sha256:39c16ad02f3db2051eaeff61e3ecb7f23a03610bc9acdc0ab5660f48582223d7
     environment:
       - NPM_CONFIG_LOGLEVEL: warn
     working_directory: ~/repo