chore(deps): Bump langgraph-checkpoint from 2.1.2 to 3.0.0

Bumps [langgraph-checkpoint](https://github.com/langchain-ai/langgraph) from 2.1.2 to 3.0.0.
- [Release notes](https://github.com/langchain-ai/langgraph/releases)
- [Commits](langchain-ai/langgraph@checkpoint==2.1.2...checkpoint==3.0.0)

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

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

Author: dependabot[bot]