Update to use actions/checkout@v4

Author: frances-h

.github/workflows/integration.yml

@@ -18,7 +18,7 @@ jobs:
           - os: macos-latest
             python-version: '3.13'
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:

.github/workflows/lint.yml

@@ -9,7 +9,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
     - name: Set up latest Python
       uses: actions/setup-python@v5
       with:

.github/workflows/readme.yml

@@ -13,7 +13,7 @@ jobs:
         python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
         os: [ubuntu-latest, macos-latest]  # skip windows bc rundoc fails
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:

.github/workflows/unit.yml

@@ -18,7 +18,7 @@ jobs:
           - os: macos-latest
             python-version: '3.13'
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with: