chore: don't support Node6 (#1976)

Author: hiroppy

azure-pipelines.yml

@@ -47,9 +47,6 @@ jobs:
         node-8:
           node_version: ^8.9.0
           webpack_version: latest
-        node-6:
-          node_version: ^6.9.0
-          webpack_version: latest
     steps:
       - task: NodeTool@0
         inputs:
@@ -98,9 +95,6 @@ jobs:
         node-8:
           node_version: ^8.9.0
           webpack_version: latest
-        node-6:
-          node_version: ^6.9.0
-          webpack_version: latest
     steps:
       - task: NodeTool@0
         inputs:
@@ -149,9 +143,6 @@ jobs:
         node-8:
           node_version: ^8.9.0
           webpack_version: latest
-        node-6:
-          node_version: ^6.9.0
-          webpack_version: latest
     steps:
       - script: 'git config --global core.autocrlf input'
         displayName: 'Config git core.autocrlf'

package.json

@@ -11,7 +11,7 @@
     "client"
   ],
   "engines": {
-    "node": ">= 6.11.5"
+    "node": ">= 8.9.0"
   },
   "scripts": {
     "lint:prettier": "prettier \"{**/*,*}.{js,json,md,yml,css}\" --list-different",