Bump actions/checkout from 2.3.5 to 2.4.0 (#75)

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>

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

.github/workflows/Documentation.yml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         julia-version: ['1.0', '1.1', '1.2', '1.3', '1.4', 'nightly']
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
       - uses: julia-actions/setup-julia@v1
         with:
           version: ${{ matrix.julia-version }}

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
           - os: macOS-latest
             julia-arch: x86
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
         with:
           fetch-depth: 0
       - uses: julia-actions/setup-julia@v1