Bump actions/checkout from 1 to 3.1.0

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 3.1.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...v3.1.0)

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

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

Author: dependabot[bot]

.github/workflows/dotnetcore.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: windows-latest
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v3.1.0
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
     - name: Build with dotnet