chore(generative_ai): remove samples migrated to genai

[XrossFox]

Description

Deletes embeddings and model tuning examples that have been migrated to use the new google-genai SDK.

Fixes b/540949366

Checklist

Testing

• I have tested this change on a live environment and verified it works as intended.

Compliance & Style

• I have followed the Sample Guidelines.
• The README is updated with all relevant information (if applicable).
• If this PR adds a new sample directory: I updated the CODEOWNERS file.

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Post-Approval Actions

• Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request removes several Python example files, tests, and configuration files related to Vertex AI text/multimodal embeddings and supervised tuning. Specifically, it deletes code examples for batch text embedding, lower-dimension embeddings, multimodal embeddings, and tuning job cancellation, along with their corresponding test suites and dependency requirements. There are no review comments, so we have no feedback to provide.

[angelcaamal]

I didn't find any references to the deleted samples on DevSite, LGTM!

[angelcaamal]

I couldn't find any references in use for this sample in devsite, LGTM

[snippet-bot]

Here is the summary of changes.

You are about to delete 4 region tags.

• generative_ai/embeddings/batch_example.py:26, tag generativeaionvertexai_embedding_batch
• generative_ai/embeddings/generate_embeddings_with_lower_dimension.py:30, tag generativeaionvertexai_embeddings_specify_lower_dimension
• generative_ai/embeddings/multimodal_example.py:27, tag generativeaionvertexai_multimodal_embedding_image_video_text
• generative_ai/model_tuning/supervised_cancel_example.py:22, tag generativeaionvertexai_cancel_tuning_job

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[amcolin]

LGTM