build: upgrade to node 20

.github/workflows/lockfileversion-check.yml

@@ -10,4 +10,4 @@ on:
 
 jobs:
   version-check:
-    uses: openedx/.github/.github/workflows/lockfile-check.yml@master
+    uses: openedx/.github/.github/workflows/lockfileversion-check-v3.yml@master

.github/workflows/node-ci.yml

@@ -11,11 +11,6 @@ on:
 jobs:
   tests:
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        node: [18, 20]
-    continue-on-error: ${{ matrix.node == 20 }}
-
     steps:
     - name: Checkout
       uses: actions/checkout@v3
@@ -24,7 +19,7 @@ jobs:
     - name: Setup Nodejs
       uses: actions/setup-node@v4
       with:
-        node-version: ${{ matrix.node }}
+        node-version-file: '.nvmrc'
 
     - name: Install dependencies
       run: npm ci

.nvmrc

@@ -1 +1 @@
-18
+20