### Description

It would be great if the date and time format of x-axis in Landing Times is `%d %b %Y, %H:%M` instead of `%d %b %Y` to see `execution_date` of task instances.

### Use case/motivation

For x-axis of all line chart using `nvd3.lineChart`, the date and time format has only date without time because its format is `%d %b %Y` by default when `x_is_date` is `True`. From what I have seen in version 1.7, the date and time format was like `%d %b %Y, %H:%M`. It has been changed as Highcharts was no longer used since version 1.8. It is simple to fix by injecting `x_axis_format="%d %b %Y, %H:%M"` where every `nvd3.lineChart` class is initialized. 

### Related issues

_No response_

### Are you willing to submit a 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)

airflow/www/views.py
"""Export variables."""
        var_dict = {}
        decoder = json.JSONDecoder()
        for var in items:
            try:
                val = decoder.decode(var.val)
            except Exception:
                val = var.val
            var_dict[var.key] = val
        response = make_response(json.dumps(var_dict, sort_keys=True, indent=4))
        response.headers["Content-Disposition"] = "attachment; filename=variables.json"
        response.headers["Content-Type"] = "application/json; charset=utf-8"
        return response
    @expose('/varimport', methods=["POST"])
    @auth.has_access([(permissions.ACTION_CAN_CREATE, permissions.RESOURCE_VARIABLE)])
    @action_logging
    def varimport(self):
        """Import variables"""
        try:
            variable_dict = json.loads(request.files['file'].read())
        except Exception:
            self.update_redirect()
            flash("Missing file or syntax error.", 'error')
            return redirect(self.get_redirect())
        else:
            suc_count = fail_count = 0
            for k, v in variable_dict.items():
                try: