Fix wrong citation format in README

[Justin900429]

The citation provided in the README has an incorrect format. The "booktitle" field is missing a left parenthesis.

In addition, I have made the following changes to improve readability:

From:

@InProceedings{Ettinger_2021_ICCV,
author={Ettinger, Scott and Cheng, Shuyang and Caine, Benjamin and Liu, Chenxi and Zhao, Hang and Pradhan, Sabeek and Chai, Yuning and Sapp, Ben and Qi, Charles R. and Zhou, Yin and Yang, Zoey and Chouard, Aur'elien and Sun, Pei and Ngiam, Jiquan and Vasudevan, Vijay and McCauley, Alexander and Shlens, Jonathon and Anguelov, Dragomir},
title={Large Scale Interactive Motion Forecasting for Autonomous Driving: The Waymo Open Motion Dataset},
booktitle={Proceedings of the IEEE/CVF International Conference on Computer Vision (ICCV)},
month={October},
year={2021},
pages={9710-9719}
}

To:

@InProceedings{Ettinger_2021_ICCV,
  author={Ettinger, Scott and Cheng, Shuyang and Caine, Benjamin and Liu, Chenxi and Zhao, Hang and Pradhan, Sabeek and Chai, Yuning and Sapp, Ben and Qi, Charles R. and Zhou, Yin and Yang, Zoey and Chouard, Aur\'elien and Sun, Pei and Ngiam, Jiquan and Vasudevan, Vijay and McCauley, Alexander and Shlens, Jonathon and Anguelov, Dragomir},
  title={Large Scale Interactive Motion Forecasting for Autonomous Driving: The Waymo Open Motion Dataset},
  booktitle={Proceedings of the IEEE/CVF International Conference on Computer Vision (ICCV)},
  month={October},
  year={2021},
  pages={9710-9719}
}

Here are the changes I made:

• Corrected the typo in the description.
• Reformated the citation to make it more readable.

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