Use the correct branch

Author: triceo

.github/workflows/performance_score_director.yml

@@ -49,6 +49,7 @@ jobs:
         with:
           repository: TimefoldAI/timefold-solver-benchmarks
           path: ./timefold-solver-benchmarks
+          ref: "ghaperf"
 
       - name: Phase 0 - Setup JDK and Maven
         uses: actions/setup-java@v4