fix (DatePicker & Cascader): fix the dropdown animation direction of cascader and datepicker

[XivLaw]

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Fix: #21802
fix the dropdown animation direction of cascader and datepicker

before

fixed

[lqzhgood]

升级以后报错了，应该是直接修改了 props placement

[Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "placement"

found in

---> <ElDatePicker> at packages/date-picker/src/picker.vue

[yangbuyiya]

尼玛的乱搞是吧