Use stable releases

The 'signed' quality is [being removed](dotnet/install-scripts#593) from the install scripts - but your usage is really just a 'stable public release' usage anyway, which is the default.

Author: baronfel

.github/workflows/dotnet.yml

@@ -44,7 +44,6 @@ jobs:
       if: matrix.os != 'self-hosted'
       with:
         dotnet-version: '8.0.x'
-        dotnet-quality: 'signed'
         source-url: ${{ env.NUGET_SERVER_URL }}
       env:
         NUGET_AUTH_TOKEN: ${{ secrets.NUGET_AUTH_TOKEN }}