Update experiments-msmarco-doc-leaderboard.md
Fixed minor typo that should address
@@ -70,7 +70,7 @@ QueriesRanked: 5193
To fetch the indexes:
```
-python -c "from pyserini.search import SimpleSearcher; SimpleSearcher.from_prebuilt_index('msmarco-doc-per-passage')"
+python -c "from pyserini.search import SimpleSearcher; SimpleSearcher.from_prebuilt_index('msmarco-doc-expanded-per-passage')"
python -c "from pyserini.search import SimpleSearcher; SimpleSearcher.from_prebuilt_index('msmarco-doc-expanded-per-doc')"
```
