[amateur-detective] Fix repo_type to local

Author: woojiahao

amateur_detective/.gitmastery-exercise.json

@@ -9,7 +9,7 @@
     "answers.txt": "answers.txt"
   },
   "exercise_repo": {
-    "repo_type": "custom",
+    "repo_type": "local",
     "repo_name": "crime-scene",
     "repo_title": null,
     "create_fork": null,