Bump actions/setup-dotnet from 1.8.0 to 1.8.1 (#1602)

Bumps [actions/setup-dotnet](https://github.com/actions/setup-dotnet) from 1.8.0 to 1.8.1.
- [Release notes](https://github.com/actions/setup-dotnet/releases)
- [Commits](actions/setup-dotnet@v1.8.0...v1.8.1)

---
updated-dependencies:
- dependency-name: actions/setup-dotnet
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

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

.github/workflows/pull-request.yml

@@ -8,7 +8,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2.3.4
-      - uses: actions/setup-dotnet@v1.8.0
+      - uses: actions/setup-dotnet@v1.8.1
         with:
           dotnet-version: '3.1.201'