feat: upgrade workflow

Author: kamilbaczek

.github/workflows/chapter-4-contracts-workflow.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with:
-          dotnet-version: 8.0.x
+          dotnet-version: 9.0.x
       - name: Add Evolutionary Architecture Nuget Source
         uses: evolutionary-architecture/evolutionary-architecture-by-example/.github@main
         with:
@@ -52,7 +52,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with:
-          dotnet-version: 8.0.x
+          dotnet-version: 9.0.x
       - name: Add Evolutionary Architecture Nuget Source
         uses: evolutionary-architecture/evolutionary-architecture-by-example/.github@main
         with: