[DOC] Dead link in bootloader's doc

[Simonbdy]

Insert the documentation link:
https://www.luos.io/docs/tools/boot#applications

Describe the issue or the suggestion:
The link the Luos engine's repository in the infobox is dead.

How would you fix the issue / which content would you add or delete?
Fix the link

Initially opened by @fleborne in Documentation repo (Luos-io/Documentation#417)