Wrong offset for America/Phoenix

**Describe the bug**
When using America/Phoenix, it gives an offset of 4 hours from UTC/ZULU/GMT, but the real offset is 7 hours.

**Expected behavior**
Expected offset is 7 hours, specifically, 420 minutes, but it outputs 240.

Full code to be ran in Node:

```
const dayjs = require('dayjs');
const customParseFormat = require('dayjs/plugin/customParseFormat')
const utc = require('dayjs/plugin/utc')
const timezone = require('dayjs/plugin/timezone')

dayjs.extend(customParseFormat)
dayjs.extend(utc)
dayjs.extend(timezone)

let date = dayjs.tz("2021/12/25", "YYYY/MM/DD", "America/Phoenix");
let date2 = dayjs.tz("2021/12/25", "YYYY/MM/DD", "zulu");

console.log(date["$d"], date["$x"]);
console.log(date2["$d"], date2["$x"]);
```

The output is:

2021-12-25T04:00:00.000Z { '$localOffset': 240, '$timezone': 'America/Phoenix' }
2021-12-25T00:00:00.000Z { '$timezone': 'zulu' }

Also, running `date.toISOString()` and `date2.toISOString()` it outputs the right strings:

2021-12-25T07:00:00.000Z
2021-12-25T00:00:00.000Z

**Information**
- Day.js Version 1.10.7
- Linux
- Node v14.19.2

Start with the timezone plugin entry point and reproduce the provided Node.js snippet for America/Phoenix on 2021/12/25. Compare the reported $localOffset with the documented 420-minute offset and the existing toISOString() output; done means the offset metadata is consistent without regressing the ISO strings.

Written by the indexing model from the issue text.