prometheus: Update the monitored link for ALPM

The project now has a centralized landing page hosted in the root
directory which we can observe instead of the docs for one specific
crate.

Related to archlinux/alpm/alpm#76
Related to archlinux/alpm/alpm!57



Signed-off-by: Christian Heusel <christian@heusel.eu>

roles/prometheus/defaults/main.yml

@@ -29,7 +29,7 @@ blackbox_targets:
 
     # regenerate the list below with: ./misc/find-arch-on-crt.sh targets
     - https://accounts.archlinux.org
-    - https://alpm.archlinux.page/alpm_buildinfo/
+    - https://alpm.archlinux.page/
     - https://america.archive.pkgbuild.com
     - https://america.mirror.pkgbuild.com
     - https://archinstall.archlinux.page