Correct output of timezone ("z") for CET/CEST

**Describe the bug**
When I am formatting the timzone with "z", I'll get a GMT+2. The date I am using is 2022-05-22, 11:00am UTC

```
dayjs(raceDate).locale(locale).format('LT z') // Output "13:00 GMT+2"
```

**Expected behavior**
I would expect CET or CEST. If I am using the long format instead, it works as expected:

```
dayjs(raceDate).locale(locale).format('LT zzz') // Output "13:00 Central European Summer Time"
```

**Information**
- Day.js Version: 1.9.7
- OS: iOS
- Browser: Safari
- Time zone: GMT+02:00 CEST

Start by reproducing the format('LT z') and format('LT zzz') examples with the supplied 2022-05-22 UTC date, then trace the timezone-formatting entry point. Done means the short format returns CET or CEST for the reported date and locale, while the long format continues to return Central European Summer Time.

Written by the indexing model from the issue text.