[User Portal, Settings] User language should prioritize user preference > browser setting

## Background:
- Device / Browser (OS version): Chrome Version 97.0.4692.71 (Official Build) (x86_64)
- Version Tag: 2022-02-08.0
- Testing site: https://demo-webapp-refresh-token.authgear-staging.com/
- Reported by: Anthony

## Description:
When the user change language to Chinese, the page does not change accordingly.

User needs to change browser language to Chinese to see the language change, which is unexpected as the prioritization should be user preference first.

## Steps to reproduce:
1. Log in to admin portal > click project "demo-webapp-refresh-token"
2. Select Localization > Enable Chinese language
3. Log in to testing site as user and go to Profile page
4. Click Preferred Language > change language to Chinese
5. See the page language not change

## Expected result:
Should prioritize user preference language > browser language setting

## Screenshot:

https://user-images.githubusercontent.com/4337525/153815719-db416828-c138-432e-8f1d-1b1e69f4aa22.mp4

Reproduce the issue at the testing site by opening the Profile page and changing Preferred Language to Chinese after enabling Chinese in the admin portal. Trace the language-selection entry point to determine why the browser setting wins over the saved user preference. Done means the page switches to the user's preferred language without changing the browser language.

Written by the indexing model from the issue text.