[csharp-netcore] Pipeline fix (#14495)

* trying to fix pipeline

* forcing pipeline to run

* reverting change to wrong branch

* forcing pipeline to run

* reverting change

Author: devhl-labs

.github/workflows/samples-dotnet-standard.yaml

@@ -21,7 +21,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-dotnet@v3.0.3
         with:
-          dotnet-version: 2.1.*
+          dotnet-version: 3.1.*
       - name: Build
         working-directory: ${{ matrix.sample }}
         run: dotnet build Org.OpenAPITools.sln