Update publish workflow

Author: hleb-albau

.github/workflows/nuget-publish.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-dotnet@v1.6.0
+      - uses: actions/setup-dotnet@v1
         with:
           dotnet-version: '3.1.x'
       - run: dotnet pack src/Regula.DocumentReader.WebClient -c Release -p:PackageVersion=${{github.event.release.name}}