[Doc Link Fix No.17] Fix rnn_design.md

[chengchen512]

修复内容

任务 1: docs/design/dynamic_rnn/rnn_design.md

• 原链接:
• http://mxnet.io/how_to/bucketing.html
• https://www.tensorflow.org/versions/r0.12/api_docs/python/contrib.training/bucketing
• 新链接:
• https://www.tensorflow.org/api_docs/python/tf/data/experimental/bucket_by_sequence_length
• https://mxnet.apache.org/versions/1.6/api/python/docs/api/module/index.html#mxnet.module.BucketingModule

验证结果

已手动访问所有更新后的链接,确认所有链接可正常访问

• 【快乐开源】PaddlePaddle 文档链接修复任务  #7735

@HZ1ovo @Echo-Nie

[paddle-bot]

感谢你贡献飞桨文档，文档预览构建中，Docs-New 跑完后即可预览，预览链接：http://preview-pr-7819.paddle-docs-preview.paddlepaddle.org.cn/documentation/docs/zh/api/index_cn.html
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[github-actions]

📚 本次 PR 文档预览链接（点击展开）

ℹ️ 预览提醒 请等待 Docs-NEW 流水线运行完成后再点击预览链接，否则可能会看到旧版本内容或遇到链接无法访问的情况。

• docs/design/dynamic_rnn/rnn_design.md: 点击预览

[Copilot]

Pull request overview

This PR fixes two broken external links in the RNN design document (docs/design/dynamic_rnn/rnn_design.md), as part of the ongoing Issue #7735 link-fixing effort. The old links pointed to outdated URLs (TensorFlow r0.12 contrib API and the legacy mxnet.io domain) that are no longer accessible.

Changes:

• Updated the TensorFlow Bucketing reference from the deprecated r0.12/contrib.training/bucketing URL to the current tf.data.experimental.bucket_by_sequence_length documentation.
• Updated the MXNet Bucketing reference from the defunct mxnet.io domain to the official mxnet.apache.org BucketingModule API page.

[Echo-Nie]

LGTM