ci: remove matrix test for node version

Author: jenssimon

.github/workflows/ci.yml

@@ -9,18 +9,13 @@ jobs:
   build:
     runs-on: ubuntu-latest
 
-    strategy:
-      matrix:
-        node-version: [18.x, 20.x]
-        # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
-
     steps:
     - uses: actions/checkout@v4
 
-    - name: Use Node.js ${{ matrix.node-version }}
+    - name: Use Node.js
       uses: actions/setup-node@v4
       with:
-        node-version: ${{ matrix.node-version }}
+        node-version-file: '.nvmrc'
         cache: 'yarn'
 
     - name: Dependencies