Correct GH Yaml syntax

Author: bladyjoker

.github/workflows/nix-flake-check.yaml

@@ -24,12 +24,11 @@ jobs:
     steps:
     - name: 📥 Checkout repository
       uses: actions/checkout@v4
-    - name: Run only on Ubuntu
+    - name: Free Disk Space (Ubuntu)
       if: matrix.os == 'ubuntu-22.04'
-      - name: Free Disk Space (Ubuntu)
-        uses: jlumbroso/free-disk-space@main
-        with:
-          tool-cache: true
+      uses: jlumbroso/free-disk-space@main
+      with:
+        tool-cache: true
     - name: 🛠️ Install Nix
       uses: cachix/install-nix-action@v21
       with: