Link added for registered "concern" does not work

[RalfJung]

Here, rfcbot added a link to a registered concern, with the URL

https://github.com/rust-lang/reference/pull/1657#issuecomment--1859695680

That link is wrong in two ways:

• there's a --, should be a - (but maybe that works anyway for some reason?)
• the ID is wrong. The correct link is https://github.com/rust-lang/reference/pull/1657#issuecomment-2435271616