Abbreviated named offset for timezone i.e "z" (small z) is not working.

**Describe the bug**
In the advance Formatting options the small 'z' is used to show the "Abbriviated named offset" like - IST for Indian Standard Time. But, this is not working.

**Expected behavior**
Using small z in format shows abbriviated named offset like IST, EST

**Information**
- Day.js Version 1.11.0
- OS: Ubuntu 22.04
- Browser Chrome 120.0.6099.109
- Time zone: GMT + 5:30 (Indian Standard Time)

Here you can see the issue in the screenshot :

Here is the codesandbox : https://codesandbox.io/s/thirsty-lamport-d8q96x?file=/src/App.js

Begin with the linked CodeSandbox and search the repository for the `z` format token and existing timezone-formatting tests. Compare the current result with the Advanced Formatting expectation; done means small `z` produces the abbreviated named offset for the supplied timezone examples and the behavior is covered by a regression test.

Written by the indexing model from the issue text.