ci: update GitHub Actions to v5

updated actions/checkout from v4 to v5
updated actions/setup-dotnet from v4 to v5

Author: georgidhristov

.github/workflows/build.yml

@@ -12,10 +12,10 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Setup .NET
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 8.0.x