[Bug Report] there is problem with first-day-of-week in calendar

[chichi12311111]

Element UI version

2.15.1

OS/Browsers version

chrome 89.0.4389.114

Vue version

2.6.12

Reproduction Link

https://codepen.io/chichi12311111/pen/VwPPBKX

Steps to reproduce

当前时间4月1日（周四），设置first-day-of-week的值为5

What is Expected?

当前时间为周五，时间向前推一个周期显示

What is actually happening?

当前日期变成了周五，时间还是4月1日

[element-bot]

Translation of this issue:

Element UI version

2.15.1

OS/Browsers version

chrome 89.0.4389.114

Vue version

2.6.12

Reproduction Link

https://codepen.io/chichi12311111/pen/VwPPBKX

Steps to reproduce

The current time is April 1 (Thursday). Set the value of first day of week to 5

What is Expected?

The current time is Friday, and the time is pushed forward one cycle

What is actually happening?

The current date is Friday, and the time is April 1