update workflow

Author: jonghough

.github/workflows/unit-test.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        dotnet-version: ["6.0.x", "7.0.x", "8.0.x"]
+        dotnet-version: ["8.0.x"]
 
     steps:
       - uses: actions/checkout@v4