Remove e-mail verification success e-mails

[sunaurus]

This is a proposed change to completely remove the "e-mail verification success" e-mails from Lemmy.

For context, when a user signs up on an instance that requires e-mail verification:

• They first receive an e-mail with a link they need to click to verify their e-mail
• On clicking this link, they are directed to their home instance, where they see an "E-mail verified" success message
• Finally, they receive a second e-mail which tells them that their e-mail has successfully been verified <---- This is the e-mail that this PR proposes to remove

Arguments for removal:

• From the perspective of users, this e-mail doesn't add a lot of value, because they receive it at the same time as the website notifies them that their e-mail was verified anyway. Basically, it's a duplicated notification, which I'm sure some users might even consider a form of spam.
• From the perspective of instance admins, this e-mail doubles the e-mail related costs of any new user. On lemm.ee, we have sent 1400 of these e-mails in the past week, which accounts for 14% of our usage cap for this month on our currently active e-mail plan.

This PR is related to #3011

[Nutomic]

Makes sense to me. You also need to remove these strings from the translations repo