add types for flux text to image model

[jasonpraful]

Minor change

Adds missing types @cf/black-forest-labs/flux-1-schnell text to image model.

Ref: https://developers.cloudflare.com/workers-ai/models/flux-1-schnell/

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[xcaptain]

good job

[jasonpraful]

Agreed @xcaptain, Raised a new PR to address that #3163