docs: fixed tiktoken link error (#14840)

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docs/docs/integrations/platforms/openai.mdx

@@ -73,7 +73,7 @@ You can also use it to count tokens when splitting documents with
 from langchain.text_splitter import CharacterTextSplitter
 CharacterTextSplitter.from_tiktoken_encoder(...)
 ```
-For a more detailed walkthrough of this, see [this notebook](/docs/modules/data_connection/document_transformers/text_splitters/tiktoken)
+For a more detailed walkthrough of this, see [this notebook](/docs/modules/data_connection/document_transformers/text_splitters/split_by_token#tiktoken)
 
 ## Document Loader