test: stop testing in Node 8

BREAKING CHANGE: Node 8 is out of maintenance since Jan 2020. We no longer test against it

Author: gr2m

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node_version: ['8', '10', '12']
+        node_version: ["10", "12"]
 
     steps:
       - uses: actions/checkout@master