chore(generative_ai): update langchain dependencies for generative_ai samples

[XrossFox]

Description

This PR fixes

• Update langchain-core to 1.4.0
• Update langchain-google-vertexai to 3.2.3
• Pin both dependencies to python 3.10 and newer

Fixes b/518888434

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request replaces the google-cloud-aiplatform and langchain-google-vertexai dependencies with google-genai and langchain-google-genai across multiple requirements files. However, the review feedback correctly identifies that these changes will break several samples—including gemma2, generative_ai/evaluation, generative_ai/rag, model_garden/gemma, and people-and-planet-ai/image-classification—because the underlying code still imports and relies on the legacy packages. You should retain the original dependencies in the affected directories to prevent import and runtime errors.

[XrossFox]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates the requirements.txt files across multiple generative_ai subdirectories to bump the versions of langchain-core and langchain-google-vertexai with a Python version constraint. However, the reviewer correctly identified that the specified versions (langchain-core==1.4.0 and langchain-google-vertexai==3.2.3) do not exist on PyPI, which will cause installation and dependency resolution to fail. It is recommended to update these to valid, existing versions as suggested.

[XrossFox]

Code Review

This pull request updates the requirements.txt files across multiple generative_ai subdirectories to bump the versions of langchain-core and langchain-google-vertexai with a Python version constraint. However, the reviewer correctly identified that the specified versions (langchain-core==1.4.0 and langchain-google-vertexai==3.2.3) do not exist on PyPI, which will cause installation and dependency resolution to fail. It is recommended to update these to valid, existing versions as suggested.

i just checked, they do exist e.e

https://pypi.org/project/langchain-google-vertexai/
https://pypi.org/project/langchain-core/

[Kef131]

LGTM

[amcolin]

LGTM!