Don't test legacy Node.js versions on GH actions

.github/workflows/ci.yml

@@ -17,26 +17,3 @@ jobs:
         uses: codecov/codecov-action@v1
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
-
-  legacy-node-version-test:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        node-version: [6.x, 8.x]
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v2
-      - name: Use Node.js latest
-        uses: actions/setup-node@v2-beta # Build Babel on latest node versions
-      - name: Build
-        run: |
-          BABEL_ENV=test-legacy make -j bootstrap
-      - name: Use Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v2-beta
-        with:
-          node-version: ${{ matrix.node-version }}
-      - name: Test on node.js ${{ matrix.node-version }}
-        # Hack: --color has supports-color@5 returned true for GitHub CI
-        # Remove once `chalk` is bumped to 4.0.
-        run: |
-          BABEL_ENV=test node ./node_modules/.bin/jest --ci --color