Update nuget.yml

Author: DoubleTK

.github/workflows/nuget.yml

@@ -21,6 +21,9 @@ jobs:
  contents: write
  # Steps represent a sequence of tasks that will be executed as part of the job
  steps:
+ - uses: actions/setup-dotnet@v4
+ with:
+ dotnet-version: '9.x'
  # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
  - uses: actions/checkout@v4
  with: