agent: Improve Gemini tool schema compatibility (#30216)

Closes #30056

Apparently the API supports the "default" field now, so we can remove
that transformation.
However, optional is not supported

See https://ai.google.dev/api/caching#Schema

Release Notes:

- agent: Improve tool schema compatibility for Gemini models
6565c091e4Bennet Bo Fenner committed on 5/8/2025, 9:06:35 AM· committed by GitHubparentd39c220
1 file changedLine totals unavailable