📝 (ChromadbRM.md): Update the return type description in the documentation

The return type description for the search function in the ChromadbRM documentation was updated to provide more detailed information about the structure of the returned object. This change will help developers understand the structure of the returned object and how to use it in their code.

Author: dominik

docs/api/retrieval_model_clients/ChromadbRM.md

@@ -34,7 +34,7 @@ Search the chromadb collection for the top `k` passages matching the given query
 - `k` (_Optional[int]_, _optional_): The number of results to retrieve. If not specified, defaults to the value set during initialization.
 
 **Returns:**
-- `dspy.Prediction`: Contains the retrieved passages, each represented as a `dotdict` with a `long_text` attribute.
+- `dspy.Prediction`: Contains the retrieved passages, each represented as a `dotdict` with schema `[{"id": str, "score": float, "long_text": str, "metadatas": dict }]`
 
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