Switch setup-node to `node-version-file

Author: thibaudcolas

.github/workflows/ci.yml

@@ -48,11 +48,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - id: nvm
-        run: echo "##[set-output name=NVMRC;]$(cat .nvmrc)"
-      - uses: actions/setup-node@v2-beta
+      - uses: actions/setup-node@v2
         with:
-          node-version: "${{ steps.nvm.outputs.NVMRC }}"
+          node-version-file: '.nvmrc'
       - uses: actions/cache@v2
         with:
           path: ~/.npm