Update packit config to use production repos & rhel-8

This builds with rhel-8, just like we do with our real repositories. It
also uses the production repositories to build. We've stopped building
in Koji so those packages are outdated. It also uses the new
foreman-devel module, which pulls in the correct NodeJS version.

It also changes the indenting to be consistent, pleasing yamllint.

.packit.yaml

@@ -5,8 +5,8 @@ specfile_path: rubygem-foreman_discovery.spec
 
 # add or remove files that should be synced
 files_to_sync:
-    - rubygem-foreman_discovery.spec
-    - .packit.yaml
+  - rubygem-foreman_discovery.spec
+  - .packit.yaml
 
 # name in upstream package repository or registry (e.g. in PyPI)
 upstream_package_name: foreman_discovery
@@ -28,11 +28,11 @@ jobs:
   - job: copr_build
     trigger: pull_request
     targets:
-      centos-stream-8:
-        additional_modules: "foreman:el8,nodejs:12"
+      rhel-8:
+        additional_modules: "foreman-devel:el8"
         additional_repos:
-          - http://koji.katello.org/releases/yum/foreman-nightly/el8/x86_64/
-          - http://yum.theforeman.org/plugins/nightly/el8/x86_64/
+          - https://yum.theforeman.org/releases/nightly/el8/x86_64/
+          - https://yum.theforeman.org/plugins/nightly/el8/x86_64/
     module_hotfixes: true
 
 srpm_build_deps: