Remove repeated example in Prometheus Adapter Spec

Contributes to
https://gitlab.com/gitlab-org/gitlab/-/issues/212541

.rubocop.yml

@@ -402,7 +402,6 @@ RSpec/RepeatedExample:
     - 'spec/models/ability_spec.rb'
     - 'spec/models/ci/build_spec.rb'
     - 'spec/models/concerns/issuable_spec.rb'
-    - 'spec/models/concerns/prometheus_adapter_spec.rb'
     - 'spec/models/member_spec.rb'
     - 'spec/models/project_services/chat_message/pipeline_message_spec.rb'
     - 'spec/models/user_spec.rb'

spec/models/concerns/prometheus_adapter_spec.rb

@@ -131,7 +131,6 @@ describe PrometheusAdapter, :use_clean_rails_memory_store_caching do
       end
 
       it { expect(subject.to_json).to eq(prometheus_data.to_json) }
-      it { expect(subject.to_json).to eq(prometheus_data.to_json) }
     end
 
     [404, 500].each do |status|