fix(api): unsubscribe all subscribed emails

[ShaunSHamilton]

Checklist:

• [x] I have read and followed the contribution guidelines.
• [x] I have read and followed the how to open a pull request guide.
• [x] My pull request targets the main branch of freeCodeCamp.
• [x] I have tested these changes either locally on my machine, or GitPod.

Related #40773 (Only to be closed, once new api is deployed)

Before	After
Unsubscribing accounts with the same email but different unsubscribeIds would result in emails still being sent	Unsubscribing accounts with the same email but different unsubscribeIds unsubscribes all accounts
All accounts with same unsubscribeId get unsubscribed	All accounts with same unsubscribeId get unsubscribed

These changes could be backported to the old/current api. However, I find it unscrupulous.