fix: Improve if syntax

.github/workflows/test.yml

@@ -81,19 +81,19 @@ jobs:
         run: npm run build
 
       - name: Remove lint-staged husky
-        if: github.ref == 'refs/heads/main'
+        if: ${{ github.ref == 'refs/heads/main' }}
         run: |
           npm uninstall lint-staged husky
           git checkout package-lock.json package.json
 
       - name: Setup mdBook
-        if: github.ref == 'refs/heads/main'
+        if: ${{ github.ref == 'refs/heads/main' }}
         uses: peaceiris/actions-mdbook@v1.1.14
         with:
           mdbook-version: '0.4.5'
 
       - name: Build site
-        if: github.ref == 'refs/heads/main'
+        if: ${{ github.ref == 'refs/heads/main' }}
         working-directory: ./test_projects/mdbook
         run: mdbook build