updated action version

Author: mfouesneau

.github/workflows/deploy.yml

@@ -15,7 +15,7 @@ jobs:
         os: [ubuntu-latest]
         python-version: [3.9]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     # Install dependencies
     - name: Set up Python ${{ matrix.python-version }}