Update introduction section in README.md

Author: lfunderburk

README.md

@@ -4,7 +4,7 @@ Building Natural Language and LLM Pipelines, First Edition</h1>
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 <h2 align="center">
-An introduction to Haystack by Deepset
+Build production-grade RAG, tool contracts, and context engineering with Haystack and LangGraph
 </h2>
 <p align="center">
 Laura Funderburk</p>