[Bug Report] DateTimePicker日期选择器设置firstDayOfWeek：3，导致部分月份日期选择后会顺延7天

### Element UI version
2.15.14

### OS/Browsers version
120.0.6099.130

### Vue version
2.7.16

### Reproduction Link
https://codepen.io/pen

### Steps to reproduce
var Main = {
data() {
return {
pickerOptions: {
firstDayOfWeek:3,
shortcuts: [{
text: '最近一周',
onClick(picker) {
const end = new Date();
const start = new Date();
start.setTime(start.getTime() - 3600 * 1000 * 24 * 7);
picker.$emit('pick', [start, end]);
}
}, {
text: '最近一个月',
onClick(picker) {
const end = new Date();
const start = new Date();
start.setTime(start.getTime() - 3600 * 1000 * 24 * 30);
picker.$emit('pick', [start, end]);
}
}, {
text: '最近三个月',
onClick(picker) {
const end = new Date();
const start = new Date();
start.setTime(start.getTime() - 3600 * 1000 * 24 * 90);
picker.$emit('pick', [start, end]);
}
}]
},
value1: '',
value2: ''
};
}
};
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')

### What is Expected?
设置firstDayOfWeek为2或者3，日期选择正常，不会顺延7天

### What is actually happening?
设置firstDayOfWeek为2或者3，日期选择正常，会顺延7天；例如：选择2023-08-06到2023-08-06实际显示的值是2023-08-13到2023-08-13，选择2022-02-06到2022-02-06实际显示的值是2022-02-13到2022-02-13