chore(multiple samples): update langchain and google-genai dependencies

[XrossFox]

Description

This PR fixes

• Replaced langchain-google-vertexai with langchain-google-genai==4.2.4; python_version >= "3.10".
• Replaced google-vertexai, google-cloud-aiplatform, and older google-genai versions with google-genai==2.7.0; python_version >= "3.10".
• Updated langchain-core to version 1.4.0 and pinned to python_version >= "3.10".

Fixes b/518888434, b/518889022 and b/518889824

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.

[gemini-code-assist]

Replacing google-cloud-aiplatform with google-genai will break this sample. The code in gemma2/gemma2_predict_gpu.py imports google.cloud.aiplatform (line 27) and uses aiplatform.gapic.PredictionServiceClient (line 51). The new google-genai SDK is a completely different package and does not provide the google.cloud.aiplatform namespace. Please keep google-cloud-aiplatform as a dependency.

google-cloud-aiplatform[all]==1.64.0

[gemini-code-assist]

Replacing google-cloud-aiplatform with google-genai will break this sample. The code in generative_ai/evaluation/pairwise_summarization_quality.py imports vertexai (line 25) and uses vertexai.init and GenerativeModel from vertexai.generative_models. These are part of the google-cloud-aiplatform package, not google-genai. Please keep google-cloud-aiplatform as a dependency.

google-cloud-aiplatform[all]==1.69.0

[gemini-code-assist]

Replacing langchain-google-vertexai with langchain-google-genai will break this sample if any code imports or uses Vertex AI-specific LangChain classes. Since this sample relies on Vertex AI, please keep langchain-google-vertexai as a dependency.

langchain-google-vertexai==1.0.10

[gemini-code-assist]

Replacing google-cloud-aiplatform with google-genai will break this sample. The code in generative_ai/rag/generate_content_example.py imports vertexai (line 29) and vertexai.rag (line 27). These modules are part of the google-cloud-aiplatform package and are not available in google-genai. Please keep google-cloud-aiplatform as a dependency.

google-cloud-aiplatform==1.87.0

[gemini-code-assist]

Replacing google-cloud-aiplatform with google-genai will break this sample. The code in model_garden/gemma/gemma3_deploy.py imports google.cloud.aiplatform (line 19) and vertexai (line 28). These are part of the google-cloud-aiplatform package and are not available in google-genai. Please keep google-cloud-aiplatform as a dependency.

google-cloud-aiplatform[all]==1.103.0

[gemini-code-assist]

Replacing google-cloud-aiplatform with google-genai will break this sample. The code in people-and-planet-ai/image-classification/predict.py imports google.cloud.aiplatform (line 21) and google.cloud.aiplatform.gapic.schema (line 22). These are part of the google-cloud-aiplatform package and are not available in google-genai. Please keep google-cloud-aiplatform as a dependency.

google-cloud-aiplatform==1.47.0