ci: don't install webpack again (#680)

Co-authored-by: Nitin Kumar <snitin315@gmail.com>

.github/workflows/nodejs.yml

@@ -81,6 +81,7 @@ jobs:
         run: npm ci
 
       - name: Install webpack ${{ matrix.webpack-version }}
+        if: matrix.webpack-version != 'latest'
         run: npm i webpack@${{ matrix.webpack-version }}
 
       - name: Run tests for webpack version ${{ matrix.webpack-version }}