Remove HipChat integration from GitLab

.rubocop_todo.yml

Gemfile

Gemfile.lock

app/models/project.rb

app/models/project_services/hipchat_service.rb

app/models/service.rb

changelogs/unreleased/52424-goodbye-hipchat.yml

config/initializers/hipchat_client_patch.rb

db/migrate/20190107151020_add_services_type_index.rb

db/migrate/20190107151029_remove_hipchat_services.rb

db/schema.rb

doc/api/services.md

doc/integration/README.md

doc/project_services/hipchat.md

doc/university/glossary/README.md

doc/user/index.md

doc/user/project/integrations/hipchat.md

doc/user/project/integrations/project_services.md

lib/api/services.rb

spec/factories/services.rb