.add or .subtract messes up an isBefore test on dayjs.tz objects

**Describe the bug**
If doing an isBefore comparison and using two dayjs objects that are both created with the timezone extension. isBefore returns False when it should be True if doing a .add or .substract first, which seems to mess everything up. Note that if you add or substract on the second object, it works fine. Check out the demo below!

**Expected behavior**
A date that is before another should return True

**Information**
- Day.js Version 1.11.7
- OS: Win11
- Browser Edge 114.0.1823.43
- Time zone: [America/Boise (GMT-7:00)]

Example (note that add and subtract return a cloned dayjs object and don't modify the originals):

```
import dayjs from 'dayjs'
import utc from 'dayjs/plugin/utc'
import tz from 'dayjs/plugin/timezone'
import customParseFormat from 'dayjs/plugin/customParseFormat'
dayjs.extend(customParseFormat)
dayjs.extend(utc)
dayjs.extend(tz)
let date1 = dayjs.tz(dayjs.utc(), 'Africa/Abidjan')
let date2 = dayjs.tz(dayjs.utc().add(1, 'minute'), 'Africa/Abidjan')

console.log('initial diff: ' + date2.diff(date1)) // 60000
console.log('diff after adding a minute', date2.add(1, 'minute').diff(date1)) // 120000
console.log('correct', date2.isBefore(date1)) // false
console.log('correct', date2.isBefore(date1.add(5, 'minute'))) // true
console.log('incorrect!', date2.subtract(5, 'minute').isBefore(date1)) // false
```

Start by running the supplied JavaScript reproduction with utc, timezone, and customParseFormat enabled. Trace isBefore after add and subtract on the timezone-created objects; done means the shown comparisons return the expected boolean values while the original objects remain unchanged.

Written by the indexing model from the issue text.