Fix RSpec/BeNil rubocop offenses

.rubocop_todo/rspec/be_nil.yml

spec/serializers/issue_entity_spec.rb

spec/serializers/member_user_entity_spec.rb

...vices/alert_management/alerts/todo/create_service_spec.rb

spec/services/groups/transfer_service_spec.rb

spec/services/merge_requests/merge_service_spec.rb

...ces/packages/ml_model/create_package_file_service_spec.rb

spec/services/packages/npm/generate_metadata_service_spec.rb

spec/services/projects/create_from_template_service_spec.rb

spec/services/projects/enable_deploy_key_service_spec.rb

...ce_desk/custom_email_verifications/create_service_spec.rb

...ervices/service_desk/custom_emails/create_service_spec.rb

...rvices/service_desk/custom_emails/destroy_service_spec.rb

spec/services/suggestions/apply_service_spec.rb

spec/services/users/untrust_service_spec.rb

...vices/users/upsert_credit_card_validation_service_spec.rb