docs: add missing link to Quickstart (langchain-ai#17085)

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- **Description:** Added missing link for Quickstart in Model IO
documentation,
  - **Issue:** N/A,
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Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

docs/docs/modules/model_io/index.mdx

@@ -17,7 +17,7 @@ A conceptual explanation of messages, prompts, LLMs vs ChatModels, and output pa
 
 ## [Quickstart](/docs/modules/model_io/quick_start)
 
-Covers the basics of getting started working with different types of models. You should walk through [this section] if you want to get an overview of the functionality.
+Covers the basics of getting started working with different types of models. You should walk through [this section](/docs/modules/model_io/quick_start) if you want to get an overview of the functionality.
 
 ## [Prompts](/docs/modules/model_io/prompts/)