[Docs] Fixed typo for --out-dir option of analyze_results.py

[jlim262]

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[yaqi0510]

jlim262，您好！您在MMClassification项目中给我们提的PR非常重要，感谢您付出私人时间帮助改进开源项目，相信很多开发者会从你的PR中受益。
我们非常期待与您继续合作，OpenMMLab专门成立了贡献者组织MMSIG，为贡献者们提供开源证书、荣誉体系和专享好礼，可通过添加微信：openmmlabwx 联系我们（请备注mmsig+GitHub id），由衷希望您能加入！

Hi @xxxx！First of all, we want to express our gratitude for your significant PR in the MMClassification project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.

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