docs: Update README.md to fix 404 links to templates (#182)

Author: chees

samples/langchain_on_vertexai/README.md

@@ -9,9 +9,9 @@ Use the following templates to deploy Retrieval Augmented Generation (RAG) appli
 
 Description | Sample
 ----------- | ------
-Deploy a pre-built `LangchainAgent` with custom RAG tool | [prebuilt_langchain_agent.py](prebuilt_langchain_agent.py)
-Build and deploy a question-answering RAG application | [retriever_chain.py](retriever_chain.p)
-Build and deploy an Agent with RAG tool and Memory | [retriever_agent_with_history.py](retriever_agent_with_history.py)
+Deploy a pre-built `LangchainAgent` with custom RAG tool | [prebuilt_langchain_agent_template.py](prebuilt_langchain_agent_template.py)
+Build and deploy a question-answering RAG application | [retriever_chain_template.py](retriever_chain_template.p)
+Build and deploy an Agent with RAG tool and Memory | [retriever_agent_with_history_template.py](retriever_agent_with_history_template.py)
 
 ## Before you begin