Bump actions/checkout from 3 to 4 (#60)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
     name: Run linters
     runs-on: "ubuntu-latest"
     steps:
-      - uses: "actions/checkout@v3"
+      - uses: "actions/checkout@v4"
       - uses: "actions/setup-python@v4"
         with:
           python-version-file: .python-version-default
@@ -47,7 +47,7 @@ jobs:
           - "pypy-3.9"
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
@@ -83,7 +83,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version-file: .python-version-default
@@ -118,7 +118,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version-file: .python-version-default
@@ -138,7 +138,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version-file: .python-version-default
@@ -153,7 +153,7 @@ jobs:
     name: Build docs & run doctests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           # Keep in sync with tox.ini/docs & .readthedocs.yaml

.github/workflows/codeql-analysis.yml

@@ -28,7 +28,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v2

.github/workflows/pypi-package.yml

@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0