Drop Node.js 4 test on CI (#6907)

.azure-pipelines/jobs/prod-test.yml

@@ -2,8 +2,6 @@ steps:
   - template: ../steps/download-dist.yml
   - template: ../steps/install-nodejs.yml
   - template: ../steps/install-dependencies.yml
-    parameters:
-      flags: --ignore-engines # prettier@dev requires node v6+
   - script: yarn test:dist
     displayName: "Run tests on dist"
   - template: ../steps/publish-test-results.yml

.azure-pipelines/steps/install-dependencies.yml

@@ -2,5 +2,5 @@ parameters:
   flags: ""
 
 steps:
-  - script: yarn install --frozen-lockfile ${{ parameters.flags }}
+  - script: yarn install --frozen-lockfile
     displayName: "Install dependencies"

.azure-pipelines/steps/install-nodejs.yml

@@ -3,8 +3,3 @@ steps:
     inputs:
       versionSpec: "$(node_version)"
     displayName: "Install Node.js"
-
-  # workaround for https://github.com/yarnpkg/yarn/issues/6900
-  - script: npm install -g yarn@1.12.3
-    displayName: "Install Node v4 compatible Yarn"
-    condition: eq(variables.node_version, 4)

azure-pipelines.yml

@@ -83,9 +83,8 @@ jobs:
       vmImage: macos-10.13
     strategy:
       matrix:
-        Node_v4:
-          node_version: 4
-          ENABLE_TEST_RESULTS: "" # jest-junit requires node v6+
+        Node_v10:
+          node_version: 10
         Node_v12:
           node_version: 12
         Node_v12_standalone: