### Apache Airflow version

Other Airflow 2 version (please specify below)

### What happened

Airflow 2.3.4 (but actual code seems to have same behaviour).

I have mapped task with xcom value.

I want to get xcom value of particular instance or xcom values of all task instances.

I am using standard REST API method /dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}/xcomEntries/{xcom_key}

And it throws an error
`
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/orm/query.py&#34;, line 2850, in one_or_none
    return self._iter().one_or_none()
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py&#34;, line 1510, in one_or_none
    return self._only_one_row(
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py&#34;, line 614, in _only_one_row
    raise exc.MultipleResultsFound(
sqlalchemy.exc.MultipleResultsFound: Multiple rows were found when one or none was required
`

Is it any way of getting xcom of mapped tasks via API?

### What you think should happen instead

_No response_

### How to reproduce

Make dag with mapped task. Return xcom value in every task. Try to get xcom value via API.

### Operating System

ubuntu 20.04

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other

### Deployment details

Standard

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

def test_should_respond_200(self):
        dag_id = "test-dag-id"
        task_id = "test-task-id"
        execution_date = "2005-04-02T00:00:00+00:00"
        execution_date_parsed = parse_execution_date(execution_date)
        run_id = DagRun.generate_run_id(DagRunType.MANUAL, execution_date_parsed)
        self._create_xcom_entries(dag_id, run_id, execution_date_parsed, task_id)
        response = self.client.get(
            f"/api/v1/dags/{dag_id}/dagRuns/{run_id}/taskInstances/{task_id}/xcomEntries",
            environ_overrides={"REMOTE_USER": "test"},
        )
        assert 200 == response.status_code
        response_data = response.json
        for xcom_entry in response_data["xcom_entries"]:
            xcom_entry["timestamp"] = "TIMESTAMP"
        assert response_data == {
            "xcom_entries": [
                {
                    "dag_id": dag_id,
                    "execution_date": execution_date,
                    "key": "test-xcom-key-1",
                    "task_id": task_id,
                    "timestamp": "TIMESTAMP",
                },
                {
                    "dag_id": dag_id,
                    "execution_date": execution_date,