Doc fixes titles (#18004)

docs/docs/getting_started/starter_example.md

-# Starter Tutorial
+# Starter Tutorial (Using OpenAI)
 
 This tutorial will show you how to get started building agents with LlamaIndex. We'll start with a basic example and then show how to add RAG (Retrieval-Augmented Generation) capabilities.
 

docs/docs/getting_started/starter_example_local.md

-# Starter Tutorial
+# Starter Tutorial (Using Local LLMs)
 
 This tutorial will show you how to get started building agents with LlamaIndex. We'll start with a basic example and then show how to add RAG (Retrieval-Augmented Generation) capabilities.