Bump .NET version in CI

Author: martinothamar

.github/workflows/dotnet-core.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 5.0.0-rc.2.20475.5
+        dotnet-version: 5.0.100-rc.2.20479.15
     - name: Install dependencies
       run: dotnet restore
     - name: Build