DEV: Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/release.yml

@@ -12,6 +12,6 @@ jobs:
     permissions:
       id-token: write
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: pipx run build
       - uses: pypa/[email protected]

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
     name: Style
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: pipx run flake8 fftl
   tests:
     name: Tests
@@ -22,7 +22,7 @@ jobs:
       matrix:
         python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
@@ -32,11 +32,11 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: pipx run build
   docs:
     name: Docs
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: pipx run --spec '.[docs]' sphinx-build -W -b html docs _build/html