Fixes #38156 - Do not call content on root during re-import

Affects only RHEL content when the repository being imported already
exists on the importing Katello instance.

This might be the case because it has been added as a "Red Hat
Repository" on both instances from a manifest file. Or else, because
this is a re-import of a newer export state to update a previously
imported state.

app/services/katello/pulp3/content_view_version/importable_repositories.rb

@@ -29,7 +29,7 @@ def generate!
 
             root = product.root_repositories.find do |r|
               if repo.content&.id && repo.redhat
-                repo_exists = r.content.cp_content_id == repo.content.id &&
+                repo_exists = r.library_instance.content.cp_content_id == repo.content.id &&
                   r.arch == repo.arch &&
                   r.major == repo.major &&
                   r.minor == repo.minor