### Description

The three commands:

```
              airflow users export /opt/airflow/dags/users.json &&
              airflow variables export /opt/airflow/dags/variables.json &&
              airflow connections export /opt/airflow/dags/connections.json
```

give back:

```
7 users successfully exported to /opt/airflow/dags/users.json
36 variables successfully exported to /opt/airflow/dags/variables.json
Connections successfully exported to /opt/airflow/dags/connections.json.
```


### Use case/motivation

Standardise output of "airflow connections export" to those of "airflow variables export" and "airflow users export"

### Related issues

_No response_

### Are you willing to submit a 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)

db_create_default_connections()
def _format_connections(conns: list[Connection], file_format: str, serialization_format: str) -> str:
    if serialization_format == "json":
        def serializer_func(x):
            return json.dumps(_connection_to_dict(x))
    elif serialization_format == "uri":
        serializer_func = Connection.get_uri
    else:
        raise SystemExit(f"Received unexpected value for `--serialization-format`: {serialization_format!r}")
    if file_format == ".env":
        connections_env = ""
        for conn in conns:
            connections_env += f"{conn.conn_id}={serializer_func(conn)}\n"
        return connections_env
    connections_dict = {}
    for conn in conns:
        connections_dict[conn.conn_id] = _connection_to_dict(conn)
    if file_format == ".yaml":
        return yaml.dump(connections_dict)
    if file_format == ".json":
        return json.dumps(connections_dict, indent=2)
    return json.dumps(connections_dict)
def _valid_uri(uri: str) -> bool: