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] <[email protected]>

Author: dependabot[bot]

.github/workflows/dotnetcore.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
 
       - name: Build
         run: dotnet build /WarnAsError

.github/workflows/release.yml

@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     steps:
-      - uses: actions/checkout@v2.3.5
+      - uses: actions/checkout@v2.4.0
 
       # Build and package everything
       - name: Package release