Revert "@event core.login_box_redirect"

This reverts commit 4eccb6b1e6e8d766451915b632f59250cfa58c17.
[ticket/12985] Add core.login_box_redirect

This is required to enable extensions to redirect a user to a specific
page when logging in.

It is required in order to replicate the "Redirect new user" mod and the
"Redirect announce" mod.