auth.userUpdate() overwrite the original object

### [REQUIRED] Step 2: Describe your environment

* Operating System version: WIN11
* Firebase SDK version: 10.3.0 (admin)
* Firebase Product: auth
* Node.js version: v16
* NPM version: _____

### [REQUIRED] Step 3: Describe the problem

#### Relevant Code:

```
console.log(body);
await auth.updateUser(param.id, body);
console.log(body);
```

#### Body before auth.updateUser
```
UserUpdateDto {
email: 'info2@basecloud.hu',
displayName: 'Basecloud',
phoneNumber: null,
role: 'user',
emailVerified: true,
disabled: false,
mfaRequired: false,
needChangePassword: false
}
```

#### Body after auth.updateUser
```
UserUpdateDto {
email: 'info2@basecloud.hu',
displayName: 'Basecloud',
emailVerified: true,
localId: '62a66160b651fe47a7cdde20',
deleteProvider: [ 'phone' ],
disableUser: false
}
```

#### Soft bug fix
```
console.log(body);
await auth.updateUser(param.id, { ...body });
console.log(body);
```

Why does the user update overwrite the original object?

Start at auth.updateUser using the provided before-and-after object reproduction, then inspect where the input object is changed during the call. Confirm that the original object remains unchanged after the update and cover that behavior with a regression test.

Written by the indexing model from the issue text.