Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/format.yaml

@@ -11,7 +11,7 @@ jobs:
     name: black
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: actions/setup-python@v5
       with:
         python-version: "3.x"

.github/workflows/pip.yaml

@@ -15,7 +15,7 @@ jobs:
         python-version: ["3.7", "3.11"]
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}

.github/workflows/wheels.yaml

@@ -14,7 +14,7 @@ jobs:
     name: Build SDist
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Build SDist
       run: pipx run build --sdist
     - name: Check metadata
@@ -32,7 +32,7 @@ jobs:
       matrix:
         os: [ubuntu-22.04, macos-13]
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: pypa/cibuildwheel@v2.17
       env:
         MACOSX_DEPLOYMENT_TARGET: 10.15