`contributing.org` has broken links

### I confirm that...

- [X] I have searched the [issue tracker](https://github.com/doomemacs/doomemacs/issues), [documentation](https://docs.doomemacs.org), [FAQ](https://docs.doomemacs.org/-/faq), [Discourse](https://discourse.doomemacs.org), and [Google](https://google.com), in case this issue has already been reported/resolved.

- [X] I have read "[How to Debug Issues](https://doomemacs.org/d/how2debug)", and will use it to provide as much information about this issue as possible.

- [X] The issue can be reproduced on the **latest** available commit of Doom.

- [X] The issue can be reproduced on a stable release of Emacs, such as 27 or 28. *(Doom does not support development builds like 29+ or any version ending in .50 or .9x)*

### Expected behavior

I expect the links to the for dev roadmap and plugins under consideration to be working (or not present).

### Current behavior

The following links don't work in [contributing.org](https://github.com/doomemacs/doomemacs/blob/master/docs/contributing.org).

```
The [development roadmap board](https://github.com/hlissner/doom-emacs/projects/3) is a rough timeline of what is being worked on and when. It will give you an idea of what will change and where you can redirect your efforts.
```

```
The [plugins under review board](https://github.com/hlissner/doom-emacs/projects/2) lists third party plugins being considered (or rejected) for inclusion in Doom Emacs. Approved and unclaimed packages are open for you to implement yourself.
```

I think `plugins under review board` is now project 5. I couldn't find a project roadmap.

### Steps to reproduce

Click on the links.

### System Information

Not relevant, since the problem is with docs.