Switch to our own mirror for aurblup

The mirrors.kernel.org mirror seems to have network issues for us from
aur.archlinux.org which makes the aurweb-aurblup service fail from time
to time. Switch to our own mirror as we are in control.

roles/aurweb/templates/config.j2

@@ -36,7 +36,7 @@ max-blob-size = 500000
 
 [aurblup]
 db-path = {{ aurweb_dir }}/aurblup
-server = https://mirrors.kernel.org/archlinux/%s/os/x86_64
+server = https://mirror.pkgbuild.com/%s/os/x86_64
 
 [mkpkglists]
 packagesfile = {{ aurweb_dir }}/web/html/packages.gz