update workflow dotnet version to 5

Author: jjw24

.github/workflows/dotnet.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v1
         with:
-          dotnet-version: 3.1.301
+          dotnet-version: 5.0.1
       - name: get version
         id: version
         uses: notiz-dev/github-action-json-property@release