Bump langgraph from 0.6.6 to 0.6.7 in the dev-dependencies group

Bumps the dev-dependencies group with 1 update: [langgraph](https://github.com/langchain-ai/langgraph).


Updates `langgraph` from 0.6.6 to 0.6.7
- [Release notes](https://github.com/langchain-ai/langgraph/releases)
- [Commits](langchain-ai/langgraph@0.6.6...0.6.7)

---
updated-dependencies:
- dependency-name: langgraph
  dependency-version: 0.6.7
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dev-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -15,7 +15,7 @@ dependencies = [
     "langchain-core>=0.3.56,<1.0.0",
     "langchain-openai==0.3.28",
     "langchain-text-splitters==0.3.11",
-    "langgraph==0.6.6",
+    "langgraph==0.6.7",
     "openai==1.93.0",
     "pgvector<=0.4.1",
     "pillow>=10.0.0",