Fixed grammar in LLM models documentation (#8210)

Description: I fixed a typo in the documentation related to LLMs
(https://python.langchain.com/docs/modules/model_io/models/llms/)

docs/docs_skeleton/docs/modules/model_io/models/llms/index.mdx

@@ -8,7 +8,7 @@ Head to [Integrations](/docs/integrations/llms/) for documentation on built-in i
 :::
 
 Large Language Models (LLMs) are a core component of LangChain.
-LangChain does not serve it's own LLMs, but rather provides a standard interface for interacting with many different LLMs.
+LangChain does not serve its own LLMs, but rather provides a standard interface for interacting with many different LLMs.
 
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