Ensure .NET9 SDK for --allow-downgrade switch on ubuntu

Author: kzu

.github/workflows/build.yml

@@ -79,6 +79,11 @@ jobs:
           name: logs
           path: '*.binlog'
 
+      - name: ⚙ dotnet
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 9.x
+
       - name: 🚀 sleet
         env:
           SLEET_CONNECTION: ${{ secrets.SLEET_CONNECTION }}

.github/workflows/publish.yml

@@ -48,6 +48,11 @@ jobs:
         working-directory: bin
         run: dotnet nuget push *.nupkg -s https://api.nuget.org/v3/index.json -k ${{secrets.NUGET_API_KEY}} --skip-duplicate
 
+      - name: ⚙ dotnet
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 9.x
+
       - name: 🚀 sleet
         env:
           SLEET_CONNECTION: ${{ secrets.SLEET_CONNECTION }}