Fix archlinux linux git redirect

It's on github not gitlab

Fix archlinux linux git redirect
1672ce54 · Jelle van der Waa · fd28fffb · 1672ce54
Verified Commit 1672ce54 authored 2 years ago by Jelle van der Waa
--- a/roles/redirects/files/maps/cgit-migrated-repos.map
+++ b/roles/redirects/files/maps/cgit-migrated-repos.map
@@ -3,3 +3,4 @@

 /netctl.git https://gitlab.archlinux.org/archlinux/netctl;
 /mkinitcpio.git https://github.com/archlinux/mkinitcpio;
+/linux.git https://github.com/archlinux/linux;