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](actions/checkout@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/build.yml

@@ -23,7 +23,7 @@ jobs:
         python-version: [3.7, 3.8, 3.9]
 
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2.2.2
       with:

.github/workflows/codeql-analysis.yml

@@ -26,7 +26,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v2.3.5
+      uses: actions/checkout@v2.4.0
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.github/workflows/python-publish.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - name: Set up Python
         uses: actions/setup-python@v2.2.2
         with: