CI: Setup .NET 6 in packages-publishing workflow (#31153)

Author: alexslavr

.github/workflows/packages_publishing.yml

@@ -43,6 +43,11 @@ jobs:
           version: 9
           run_install: false
 
+      - name: Set up .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 6.0.x
+
       - name: Get pnpm store directory
         shell: bash
         run: |