Bump langgraph-checkpoint

Bumps [langgraph-checkpoint](https://github.com/langchain-ai/langgraph) from 2.0.8 to 3.0.0.
- [Release notes](https://github.com/langchain-ai/langgraph/releases)
- [Commits](langchain-ai/langgraph@checkpoint==2.0.8...checkpoint==3.0.0)

---
updated-dependencies:
- dependency-name: langgraph-checkpoint
  dependency-version: 3.0.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

ai/gen-ai-agents/assistant-secretary-agent/files/local_requirements.txt

@@ -38,7 +38,7 @@ langchain-core==0.3.29
 langchain-experimental==0.3.4
 langchain-text-splitters==0.3.9
 langgraph==0.2.62
-langgraph-checkpoint==2.0.8
+langgraph-checkpoint==3.0.0
 langgraph-sdk==0.1.51
 langsmith==0.2.11
 markdown-it-py==3.0.0