update unittest.yml to only run tests of one test project

.github/workflows/unittest.yml

@@ -35,4 +35,5 @@ jobs:
     - name: Build
       run: dotnet build TestLSAnalyzer --no-restore
     - name: Test
+      working-directory: ./TestLSAnalyzer
       run: dotnet test --no-build --verbosity quiet --filter FullyQualifiedName!=TestLSAnalyzerUI