### Apache Airflow version

2.6.1

### What happened

When playing around with the form features as interoduced in AIP-50 and using the select list option via `enum` I realized that the default value will not be correctly picked when the form is loaded. Instead the first value always will be pre-selected.

### What you think should happen instead

Default value should be respected

### How to reproduce

Modify the `airflow/example_dags/example_params_ui_tutorial.py:68` and change the default to some other value. Load the form and see that `value 1` is still displayed on form load.

### Operating System

Ubuntu 20.04

### Versions of Apache Airflow Providers

not relevant

### Deployment

Official Apache Airflow Helm Chart

### Deployment details

not relevant

### Anything else

Workaround: Make your default currently top of the list.

### Are you willing to submit PR?

- [X] 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)

<script lang="javascript">
                const hex_chars = "0123456789ABCDEF";
                function i2hex(name) {
                    var i = document.getElementById(name).value;
                    return hex_chars.substr(parseInt(i / 16), 1) + hex_chars.substr(parseInt(i % 16), 1)
                }
                function u_{name}() {
                    var hex_val = "#"+i2hex("r_{name}")+i2hex("g_{name}")+i2hex("b_{name}");
                    document.getElementById("{name}").value = hex_val;
                    document.getElementById("preview_{name}").style.background = hex_val;
                    updateJSONconf();
                }
                function hex2i(text) {
                    return hex_chars.indexOf(text.substr(0,1)) * 16 + hex_chars.indexOf(text.substr(1,1));
                }
                function v_{name}() {
                    var value = document.getElementById("{name}").value.toUpperCase();
                    document.getElementById("r_{name}").value = hex2i(value.substr(1,2));
                    document.getElementById("g_{name}").value = hex2i(value.substr(3,2));
                    document.getElementById("b_{name}").value = hex2i(value.substr(5,2));
                    document.getElementById("preview_{name}").style.background = value;
                }
                v_{name}();
            </script>""",
            section="Special advanced stuff with form fields",
        ),
    },
) as dag:
    @task(task_id="show_params")
    def show_params(**kwargs) -> None: