'Notify me about token promotions' switch doesn't work if you've already said 'Maybe Later'

[LaurenWags]

Description

If you are prompted for a promotion and you select 'Maybe Later', the remindTimestamp is set to remind you 24h later. If you then go into Adv Settings and toggle 'Notify me about token promotions' off, you will still be reminded 24h later.

Steps to Reproduce

1. Clean install of 0.20 using ledger_environment=staging.
2. Get notification.
3. Select Maybe Later.
4. Go to Adv Settings, toggle 'Notify me about token promotions' off.
5. Close Brave.
6. Open session-store-1 and locate remindTimestamp. Using https://www.epochconverter.com/ you can see that it is set to 24h later.
7. Change this value to 5-10 minutes from now.
8. Relaunch Brave (make sure you still use ledger_env staging)

Actual result:
In 30-60 minutes you will be notified about the promotion again.

Expected result:
You should not be notified about the promotion since you toggled the switch to off.

Reproduces how often:
Easily

Brave Version

about:brave info:
0.20.30

Reproducible on current live release:
Yes

Additional Information

Missed when testing #12313

[LaurenWags]

Removed QA/checked labels due to changes in milestones. Please recheck with 0.21.15 and higher.

[kjozwiak]

Before going through verification, I reproduced the original issue using 0.20.30 8b78402 with the STR that @LaurenWags provider above.

Verified using 0.21.18 580be78 under Ubuntu 17.10 x64.