Fix amazon linux bootstrap (#11139)

c58497cde (Refactor bootstrap-os (#10983), 2024-03-27) refactored the
boostrap-os include but didn't adapt the amazon linux tasks to the
actual ID of amazon linux ('amzn')

Re-enable the CI so we can avoid that kind of breakage.

roles/bootstrap-os/tasks/amzn.yml

@@ -0,0 +1,13 @@
+---
+- name: Enable EPEL repo for Amazon Linux
+  yum_repository:
+    name: epel
+    file: epel
+    description: Extra Packages for Enterprise Linux 7 - $basearch
+    baseurl: http://download.fedoraproject.org/pub/epel/7/$basearch
+    gpgcheck: yes
+    gpgkey: http://download.fedoraproject.org/pub/epel/RPM-GPG-KEY-EPEL-7
+    skip_if_unavailable: yes
+    enabled: yes
+    repo_gpgcheck: no
+  when: epel_enabled