chore(deps): update circleci/node:8 docker digest to af6b534

Author: renovate-bot

.circleci/config.yml

@@ -6,7 +6,7 @@ machine:
 jobs:
   build:
     docker:
-      - image: circleci/node:8@sha256:503eab56f95494a9d41cff5e7f42143e0a76b94a9a0f23c300b16dbe41fd5106
+      - image: circleci/node:8@sha256:af6b534e92770b106c39201d6db2f93ce4ba34dac423f0aa79727baa533aa4e8
       - image: mongo:3.7.9@sha256:fbc5b316430a970543d2e1668164c764977e777a74ffb05c873d0e5df499b6fb
     environment:
       - NPM_CONFIG_LOGLEVEL: warn