ci(docker): update node docker digests in circleci

Author: renovate-bot

.circleci/config.yml

@@ -21,17 +21,17 @@ commands:
 jobs:
   node-v6:
     docker:
-      - image: circleci/node:6@sha256:f7c806c391e4b2fcc12cf44e7951cd9b0ab399bbc8a9395ac23e8aa2c09e3b20
+      - image: circleci/node:6@sha256:f0cfe896ff27b843ac5686ec59fe7e161e23394f853306d6eb11d1d958165c77
     steps:
       - run-npm-test
   node-v8:
     docker:
-      - image: circleci/node:8@sha256:6e75f82ff3cbeb4e7ff2c87324de30b90624678b3989a005fd3febcdaeae6987
+      - image: circleci/node:8@sha256:c81e5c1471c1012822dc92bb3c787118550e5e038b4807c9a9626f0d5deeb0b5
     steps:
       - run-npm-test
   node-v10:
     docker:
-      - image: circleci/node:10@sha256:b1cf95e9e08adc6cd622eb85c0ac77fb4836819c6c9704c5c6d72bd7fa844242
+      - image: circleci/node:10@sha256:496ee37950d199f1525fa51393f76ab25b880a6db0e64e1209f81ced120b8254
     steps:
       - run-npm-test