make passing grade 80% and consistent with other applications

app.py

@@ -12,7 +12,7 @@ from huggingface_hub import whoami
 
 EXAM_DATASET_ID = os.getenv("EXAM_DATASET_ID") or "agents-course/unit_1_quiz"
 EXAM_MAX_QUESTIONS = os.getenv("EXAM_MAX_QUESTIONS") or 10
-EXAM_PASSING_SCORE = os.getenv("EXAM_PASSING_SCORE") or 0.7
+EXAM_PASSING_SCORE = os.getenv("EXAM_PASSING_SCORE") or 0.8
 
 ds = load_dataset(EXAM_DATASET_ID, split="train")