[Bug Report] When the clearable property of DateTimePicker is set to false, it is not possible to hide the clear button in the popup layer

### Element UI version
2.15.14

### OS/Browsers version
Chrome 130.0.6723.117

### Vue version
2.7.16

### Reproduction Link
https://github.com/ElemeFE/element/tree/dev/packages

### Steps to reproduce
When the clearable property of the DateTimePicker date and time range selector is set to false, it indicates that I do not want users to be able to clear the input field. However, there is still a 'Clear' button next to the 'Confirm' button in the bottom right corner of the calendar

### What is Expected?
The clear button is hidden

### What is actually happening?
none