Ignore Repository::AmbiguousRefError in db/fixtures/development

Signed-off-by: Rémy Coutable <remy@rymai.me>

db/fixtures/development/10_merge_requests.rb

@@ -27,6 +27,9 @@ Gitlab::Seeder.quiet do
 
       Sidekiq::Worker.skipping_transaction_check do
         MergeRequests::CreateService.new(project, developer, params).execute
+      rescue Repository::AmbiguousRefError
+        # Ignore pipelines creation errors for now, we can doing that after
+        # https://gitlab.com/gitlab-org/gitlab-ce/issues/55966. will be resolved.
       end
       print '.'
     end