quote string, again

Author: atzhukov

.github/workflows/ci.yaml

@@ -25,7 +25,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
       - name: Install dependencies
-        if: matrix.os == "ubuntu-latest"
+        if: matrix.os == 'ubuntu-latest'
         run: |
           sudo apt-get update
           sudo apt-get install -y cups libcups2-dev libclang-dev