[doc] fix reranker index (#4921)

Author: hjh0119

docs/source/index.rst

@@ -49,6 +49,7 @@ Swift DOCUMENTATION
    BestPractices/GRPO代码训练.md
    BestPractices/Qwen3最佳实践.md
    BestPractices/Embedding训练.md
+   BestPractices/Reranker训练.md
    BestPractices/快速训练VL模型.md
    BestPractices/NPU支持.md
    BestPractices/更多最佳实践.md

docs/source_en/index.rst

@@ -51,6 +51,7 @@ Swift DOCUMENTATION
    BestPractices/GRPO-Code-Training.md
    BestPractices/Qwen3-Best-Practice.md
    BestPractices/Embedding.md
+   BestPractices/Reranker.md
    BestPractices/Rapidly-Training-VL-model.md
    BestPractices/NPU-support.md
    BestPractices/More-Best-Practices.md