fix(ci): Add missing setup-python step to the old copyright check (en…

…dless-sky#10621)

.github/workflows/projects_check.yml

@@ -39,6 +39,9 @@ jobs:
     - uses: actions/checkout@v4
       with:
         show-progress: false
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.x'
     - name: Install dependencies
       run: pip install --break-system-packages python-debian
     - name: Validate copyright file with python-debian