chore(deps): bump actions/checkout from 2 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

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

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

Author: dependabot[bot]

.github/workflows/publish-docs.yml

@@ -16,8 +16,8 @@ jobs:
         python-version: [3.7]
 
     steps:
-    - uses: actions/checkout@v2
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
+    - uses: actions/checkout@v4
     - run: |
         git fetch origin gh-pages
     - name: Set up Python ${{ matrix.python-version }}

.github/workflows/release.yml

@@ -11,7 +11,7 @@ jobs:
     if: ${{ github.event.workflow_run.conclusion == 'success' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           persist-credentials: false
       - name: Setup Node.js

.github/workflows/run-tests.yml

@@ -18,7 +18,7 @@ jobs:
       DEBUG_PROXY: 1
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v1
         with: