Fix the notebook links in the tutorial readme. (#154)

Co-authored-by: Jyun-Yu Jiang <[email protected]>

tutorials/kdd22/README.md

@@ -15,10 +15,10 @@ By the end of the tutorial, we believe that attendees will be easily capable of
 |---|---|---|
 | 8:00 AM - 8:30 AM | Check-in and Environment Setup | |
 | 8:30 AM - 8:50 AM | Session 1: Introduction to PECOS | |
-| 8:50 AM - 9:30 AM  | Session 2: Extreme Multi-label Ranking with PECOS | [Notebook](https://github.com/amzn/pecos/blob/tutorials/kdd22/Session%202%20Extreme%20Multi-label%20Ranking%20with%20PECOS.ipynb) |
+| 8:50 AM - 9:30 AM  | Session 2: Extreme Multi-label Ranking with PECOS | [Notebook](https://github.com/amzn/pecos/blob/mainline/tutorials/kdd22/Session%202%20Extreme%20Multi-label%20Ranking%20with%20PECOS.ipynb) |
 | 9:30 AM - 10:00 AM | Coffee Break | | 
-| 10:00 AM - 10:30 AM | Session 3: Approximate Nearest Neighbor (ANN) Search in PECOS | [Notebook](https://github.com/amzn/pecos/blob/tutorials/kdd22/Session%203%20Approximate%20Nearest%20Neighbor%20Search%20in%20PECOS.ipynb) |
-| 10:30 AM - 11:10 AM | Session 4: Utilities in PECOS | [Notebook](https://github.com/amzn/pecos/blob/tutorials/kdd22/Session%204%20Utilities%20in%20PECOS) |
-| 11:10 AM - 11:40 AM | Session 5: XR-Transformer cookbook and Distributed PECOS | [Notebook](https://github.com/amzn/pecos/blob/tutorials/kdd22/Session%205%20XR-Transformer%20cookbook%20and%20Distributed%20PECOS) |
+| 10:00 AM - 10:30 AM | Session 3: Approximate Nearest Neighbor (ANN) Search in PECOS | [Notebook](https://github.com/amzn/pecos/blob/mainline/tutorials/kdd22/Session%203%20Approximate%20Nearest%20Neighbor%20Search%20in%20PECOS.ipynb) |
+| 10:30 AM - 11:10 AM | Session 4: Utilities in PECOS | [Notebook](https://github.com/amzn/pecos/blob/mainline/tutorials/kdd22/Session%204%20Utilities%20in%20PECOS.ipynb) |
+| 11:10 AM - 11:40 AM | Session 5: XR-Transformer cookbook and Distributed PECOS | [Notebook](https://github.com/amzn/pecos/blob/mainline/tutorials/kdd22/Session%205%20XR-Transformer%20cookbook%20and%20Distributed%20PECOS.ipynb) |
 | 11:40 AM - 11:50 AM | Session 6: Research with PECOS | |
 | 11:50 AM - 12:00 PM | Closing Remarks | |