local-tokenizer does not support gemini-3-flash-preview

[fasfsfgs]

Just like #1784, but for gemini-3-flash-preview.

Environment details

• Programming language: python
• OS: macOS Tahoe 26.1
• Language runtime version: 3.12.12
• Package version: 1.59.0

Steps to reproduce

Try to count tokens for gemini-3-flash-preview with local-tokenizer:

from google.genai.local_tokenizer import LocalTokenizer
from google.genai.types import CountTokensResult

tokenizer = LocalTokenizer(model_name="gemini-3-flash-preview")
result: CountTokensResult = tokenizer.count_tokens("test")

ValueError: Model gemini-3-flash-preview is not supported. Supported models: gemini-2.5-pro, gemini-2.5-flash, gemini-2.5-flash-lite, gemini-2.0-flash, gemini-2.0-flash-lite, gemini-2.5-pro-preview-06-05, gemini-2.5-pro-preview-05-06, gemini-2.5-pro-exp-03-25, gemini-live-2.5-flash, gemini-2.5-flash-preview-05-20, gemini-2.5-flash-preview-04-17, gemini-2.5-flash-lite-preview-06-17, gemini-2.0-flash-001, gemini-2.0-flash-lite-001, gemini-3-pro-preview.

[fasfsfgs]

I've opened a PR to address this: #1973