ci: update checkout to v4

Author: CJ Steiner

.github/workflows/deploy.yml

@@ -12,7 +12,7 @@ jobs:
   pr:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/setup-python@v4
       with:
         python-version: 3.x