43062: Updated the gemma tokenizer docstring and added a separate test to verify
Author: vaibhav-research
Pull request: yes

# What does this PR do?
This PR clarifies the behavior of GemmaTokenizerFast.
The fast tokenizer normalizes spaces to "▁" and does not apply an additional whitespace pre-tokenizer (pre_tokenizer=None).

The change adds a brief docstring clarification and a small test to document and lock in this behavior, addressing the confusion raised in #43062

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Fixes # 43062


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Comments:
CI is failing in the PR slow CI – Suggestion workflow at the step “Get PR commit SHA / Get PR commit SHA better” with HttpError: No commit found for SHA:.
This appears unrelated to the code changes and happens before any tests run.
I retriggered CI, but the issue persists, likely a workflow context issue.