[Email login] Registered email cannot be used after enable and disable ignore dot function

## Background:
- Device / Browser (OS version): iPhone 11 Pro IOS 14.5
- Build: Version 1.0 (1622188340) May 28,2021 at 15:56

## Description:
Inconsistent behaviour for registered email that contains dot(.) in local part.

## Steps to reproduce:
1. Tick "Ignore dot(.) in local part" in web portal
2. Sign up using an email that contains dot in local part (e.g. a.bcd1533aa.b@gmail.com )
3. Received email and register successfully
4. Able to login using the original email (a.bcd1533aa.b@gmail.com) and original email without dot (abcd1533aab@gmail.com)
5. Untick "Ignore dot(.) in local part"
6. cannot use original email (i.e. a.bcd1533aa.b@gmail.com) to login, 'invalid credentials' displayed
7. however, abcd1533aab@gmail.com can be used to login
8. after login , the original email is displayed

## Expected result:
After "Ignore dot(.) in local part" is disabled, user should be able to login using their original email that contains dot(.)

## Screenshot: