fix: fix error introduced in multi-observable execution

Author: hJaffaliColibritd

mpqp/execution/providers/ibm.py

@@ -487,27 +487,7 @@ def run_aer(job: Job):
         result = extract_result(result_sim, job, job.device)
 
     elif job.job_type == JobType.OBSERVABLE:
-        if isinstance(job.device, (IBMDevice, IBMSimulatedDevice)):
-
-            results = []
-
-            for _ in job.measure.observables:
-                expectation_value = compute_expectation_value(
-                    qiskit_circuit, job, backend_sim
-                )
-
-                if isinstance(expectation_value, BatchResult):
-                    results.extend(expectation_value.results)
-                elif isinstance(expectation_value, Result):
-                    results.append(expectation_value)
-                else:
-                    raise TypeError(
-                        f"compute_expectation_value() returned {type(expectation_value)}, expected Result or BatchResult."
-                    )
-
-                # results.append(expectation_value)
-
-            result = BatchResult(results) if len(results) > 1 else results[0]
+        result = compute_expectation_value(qiskit_circuit, job, backend_sim)
 
     else:
         raise ValueError(f"Job type {job.job_type} not handled.")