Add duration not working anymore

**Describe the bug**
In the following code:

```
const duration = dayjs.duration({ weeks: 1 });
const initialDate = dayjs(date);
const result = initialDate.add(duration);
```

`initialDate` and `result ` resolve to the same date.

This happened after upgrading from dayjs `1.11.8` to `1.11.9` or `1.11.10`

**Expected behavior**
The `result` date is correctly calculated

**Information**
- Day.js Version [1.11.9+]
- OS: [OS X 14.0]-
- Time zone: [GMT+1]

Start by reproducing the provided dayjs.duration({ weeks: 1 }) and initialDate.add(duration) example on Day.js 1.11.9 or newer, then compare it with 1.11.8. The work is done when adding a one-week duration changes the date as expected and the regression is verified against the reported versions.

Written by the indexing model from the issue text.