update workflow action versions

Author: nedbat

.github/workflows/tests.yml

@@ -50,10 +50,12 @@ jobs:
 
     steps:
       - name: "Check out the repo"
-        uses: "actions/checkout@v3"
+        uses: "actions/checkout@v4"
+        with:
+          persist-credentials: false
 
       - name: "Set up Python"
-        uses: "actions/setup-python@v4"
+        uses: "actions/setup-python@v5"
         with:
           python-version: "${{ matrix.python-version }}"
           allow-prereleases: true
@@ -85,10 +87,12 @@ jobs:
 
     steps:
       - name: "Check out the repo"
-        uses: "actions/checkout@v2"
+        uses: "actions/checkout@v4"
+        with:
+          persist-credentials: false
 
       - name: "Set up Python"
-        uses: "actions/setup-python@v2"
+        uses: "actions/setup-python@v5"
         with:
           python-version: "3.8"