Can't change email for group notifications

Summary

When I try to change my email in notification settings for specific groups, it gives a 404 error. This is caused by the urls using %2F instead of a / (slash) (I confirmed this by using a curl and only editing the slashes in the url).

Steps to Reproduce

1. https://gitlab.com/-/profile/notifications
2. Try to change your email for any groups you have (you need to have more than 1 email addresses)
3. 404