Bump actions/checkout from 2.3.5 to 2.4.0

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.3.5 to 2.4.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2.3.5...v2.4.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/autofix.yaml

@@ -16,7 +16,7 @@ jobs:
     name: Format markdown, update TOC and create a PR
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - name: Install doctoc
         run: |
           sudo npm install -g doctoc
@@ -65,7 +65,7 @@ jobs:
     name: Format JSON files and create a PR
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - name: Install linter
         run: |
           sudo npm install jsonlint -g
@@ -92,7 +92,7 @@ jobs:
     name: Fix typos and create a PR
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - uses: sobolevn/misspell-fixer-action@0.1.0
       - uses: peter-evans/create-pull-request@v3.10.1
         with:
@@ -113,7 +113,7 @@ jobs:
     name: Optimize images
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - uses: calibreapp/image-actions@1.1.0
         id: image_actions
         with:

.github/workflows/labels_sync.yaml

@@ -8,7 +8,7 @@ jobs:
     name: Sync labels
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - uses: lannonbr/issue-label-manager-action@3.0.0
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/lint.yaml

@@ -13,7 +13,7 @@ jobs:
     name: Lint markdown
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - uses: avto-dev/markdown-lint@v1.5.0
         with:
           config: '.github/markdown-lint.yaml'
@@ -23,7 +23,7 @@ jobs:
     name: Lint Awesome list
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
         with:
           # Fetch all history to please linter's age checks.
           fetch-depth: 0
@@ -35,7 +35,7 @@ jobs:
     name: Lint YAML files
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - uses: actions/setup-python@v2.2.2
       - name: Install linter
         run: |