stdlib: Remove 'additional_params' value type assert

The value of a `WorkloadResource`'s additional parameter may not always
be a string. It can be any JSON value (integer, a list, a dict, ect.).
For Looppoint resources we have additional parameters such as a List of
region start points.

The assert inside workloads checking the type of the value breaks
certain usecase and is therefore removed in this commit.

Change-Id: Iecb1518082c28ab3872a8de888c76f0800261640

src/python/gem5/resources/resource.py

@@ -1098,7 +1098,6 @@ def obtain_resource(
             for key in resource_json["additional_params"].keys():
                 assert isinstance(key, str)
                 value = resource_json["additional_params"][key]
-                assert isinstance(value, str)
                 params[key] = value
         resource_json["parameters"] = params
     # Once we know what AbstractResource subclass we are using, we create it.