Recover video models dir structure (#2028)

fluid/PaddleCV/video/models/attention_cluster/README.md

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+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/attention_cluster](../../../../../PaddleCV/video/models/attention_cluster/) 目录下浏览本项目。

fluid/PaddleCV/video/models/attention_lstm/README.md

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+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/attention_lstm](../../../../../PaddleCV/video/models/attention_lstm/) 目录下浏览本项目。

fluid/PaddleCV/video/models/nextvlad/README.md

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+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/nextvlad](../../../../../PaddleCV/video/models/nextvlad/) 目录下浏览本项目。

fluid/PaddleCV/video/models/nonlocal_model/README.md

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+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/nonlocal_model](../../../../../PaddleCV/video/models/nonlocal_model/) 目录下浏览本项目。

fluid/PaddleCV/video/models/stnet/README.md

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+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/stnet](../../../../../PaddleCV/video/models/stnet/) 目录下浏览本项目。

fluid/PaddleCV/video/models/tsm/README.md

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+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/tsm](../../../../../PaddleCV/video/models/tsm/) 目录下浏览本项目。

fluid/PaddleCV/video/models/tsn/README.md

+
+您好，该项目已被迁移，请移步到 [PaddleCV/video/models/tsn](../../../../../PaddleCV/video/models/tsn/) 目录下浏览本项目。