Add pipeline_email_service. Fixes:

https://gitlab.com/gitlab-org/gitlab-ce/builds/4710913

spec/lib/gitlab/import_export/all_models.yml

@@ -125,6 +125,7 @@ project:
 - drone_ci_service
 - emails_on_push_service
 - builds_email_service
+- pipelines_email_service
 - irker_service
 - pivotaltracker_service
 - hipchat_service
@@ -184,4 +185,4 @@ project:
 - project_feature
 award_emoji:
 - awardable
-- user
+- user
\ No newline at end of file