fix: send embedding_model as query parameter in fileSearchStores.create

[kausmeows]

PR Description

What the EAP docs say should work:

store = client.file_search_stores.create(
    config={
        "display_name": "Multimodal Catalog",
        "embedding_model": "models/gemini-embedding-2"
    }
)

What the SDK does in v1.75.0 (broken):

The serializer _CreateFileSearchStoreConfig_to_mldev places embeddingModel in the request body: setv(parent_object, ['embeddingModel'], ...)

This sends:

POST /v1beta/fileSearchStores
Body: {"displayName": "...", "embeddingModel": "models/gemini-embedding-2"}

The API rejects it:

400 INVALID_ARGUMENT. Invalid JSON payload received.
Unknown name "embeddingModel" at 'file_search_store': Cannot find field.

Seems like a regression from- kausmeows@dd11222 ?

Because as per EAP the API still accepts it as query. With this fix the integration is working in Agno. Had to monkey patch here rn- agno-agi/agno#7788

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[kausmeows]

not needed, as the google team decided to keep this and update the API.