Update build.yml

.github/workflows/build.yml

@@ -15,8 +15,6 @@ jobs:
     - uses: actions/checkout@v2
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
-      with:
-        dotnet-version: 5.0.100
     - name: Install dependencies
       run: dotnet restore
     - name: Build