Update langchain-google-vertexai requirement

Updates the requirements on [langchain-google-vertexai](https://github.com/langchain-ai/langchain-google) to permit the latest version.
- [Release notes](https://github.com/langchain-ai/langchain-google/releases)
- [Commits](langchain-ai/langchain-google@libs/vertexai/v0.0.6rc0...libs/genai/v3.0.0)

---
updated-dependencies:
- dependency-name: langchain-google-vertexai
  dependency-version: 3.0.0
  dependency-type: direct:production
...

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Author: dependabot[bot]

topic/machine-learning/langchain/requirements.txt

@@ -3,7 +3,7 @@ cratedb-about==0.0.8
 google-cloud-aiplatform<2
 langchain-cratedb<0.1.2
 langchain-mcp-adapters<0.2
-langchain-google-vertexai<3
+langchain-google-vertexai<4
 langchain-openai<0.4
 langchain-text-splitters<0.4
 langgraph<0.7