chore: bump pypdf from 4.3.0 to 6.0.0 in /examples/langchain_rag (#270)

Author: dependabot[bot]

examples/langchain_rag/requirements.txt

@@ -9,4 +9,4 @@ httpx==0.27.2
 beautifulsoup4==4.12.3
 chromadb==0.5.4
 uvicorn==0.30.1
-pypdf==4.3.0
+pypdf==6.0.0