[Fix] Citations format of ANN

[MengzhangLI]

Modification:
From

@inproceedings{annn,
  author    = {Zhen Zhu and
               Mengde Xu and
               Song Bai and
               Tengteng Huang and
               Xiang Bai},
  title     = {Asymmetric Non-local Neural Networks for Semantic Segmentation},
  booktitle={International Conference on Computer Vision},
  year      = {2019},
  url       = {http://arxiv.org/abs/1908.07678},
}

to

@inproceedings{zhu2019asymmetric,
  title={Asymmetric non-local neural networks for semantic segmentation},
  author={Zhu, Zhen and Xu, Mengde and Bai, Song and Huang, Tengteng and Bai, Xiang},
  booktitle={Proceedings of the IEEE/CVF International Conference on Computer Vision},
  pages={593--602},
  year={2019}
}

[codecov]

Codecov Report

Merging #759 (b93eadb) into master (6394679) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##           master     #759   +/-   ##
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  Coverage   85.37%   85.37%           
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  Files         107      107           
  Lines        5847     5847           
  Branches      960      960           
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  Hits         4992     4992           
  Misses        673      673           
  Partials      182      182           

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[Junjun2016]

LGTM