gemini: Fix issue with builtin tool schemas (cherry-pick #33917) (#33919)
gcp-cherry-pick-bot[bot]
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Bennet Bo Fenner
created
Cherry-picked gemini: Fix issue with builtin tool schemas (#33917)
Closes #33894
After #33635 Gemini Integration was broken because we now produce
`const` fields for enums, which are not supported.
Changing this to `openapi3` fixes the issue.
Release Notes:
- Fixed an issue where Gemini Models would not work because of
incompatible tool schemas
Co-authored-by: Bennet Bo Fenner <bennet@zed.dev>