Add concurency_limit parameter to WMLInferenceEngine

[elronbandel]

Closes: #1215

[allyssonf]

@elronbandel , looks good to me. But is it possible to update the documentation adding this new parameter?

class WMLInferenceEngine(
    InferenceEngine, WMLInferenceEngineParamsMixin, PackageRequirementsMixin
):
    """Runs inference using ibm-watsonx-ai.

    Attributes:
        credentials (Dict[str, str], optional): By default, it is created by a class
            instance which tries to retrieve proper environment variables
            ("WML_URL", "WML_PROJECT_ID", "WML_APIKEY"). However, a dictionary with
            the following keys: "url", "apikey", "project_id" can be directly provided
            instead.
        model_name (str, optional): ID of a model to be used for inference. Mutually
            exclusive with 'deployment_id'.
        deployment_id (str, optional): Deployment ID of a tuned model to be used for
            inference. Mutually exclusive with 'model_name'.
        parameters (WMLInferenceEngineParams, optional): Instance of WMLInferenceEngineParams
            which defines inference parameters and their values. Deprecated attribute, please
            pass respective parameters directly to the WMLInferenceEngine class instead.
       concurrency_limit (int): number of requests that will be sent in parallel, max is 10. 

[pawelknes]

lgtm

[elronbandel]

Done @allyssonf.