remove spec for non-existent endpoint

spec/controllers/projects/issues_controller_spec.rb

@@ -877,46 +877,4 @@ describe Projects::IssuesController do
                                   format: :json
     end
   end
-
-  describe 'GET #discussions' do
-    let!(:discussion) { create(:discussion_note_on_issue, noteable: issue, project: issue.project) }
-    context 'when authenticated' do
-      before do
-        project.add_developer(user)
-        sign_in(user)
-      end
-
-      it 'returns discussion json' do
-        get :discussions, namespace_id: project.namespace, project_id: project, id: issue.iid
-
-        expect(json_response.first.keys).to match_array(%w[id reply_id expanded notes individual_note])
-      end
-    end
-
-    context 'with cross-reference system note', :request_store do
-      let(:new_issue) { create(:issue) }
-      let(:cross_reference) { "mentioned in #{new_issue.to_reference(issue.project)}" }
-
-      before do
-        create(:discussion_note_on_issue, :system, noteable: issue, project: issue.project, note: cross_reference)
-      end
-
-      it 'does not result in N+1 queries' do
-        # Instantiate the controller variables to ensure QueryRecorder has an accurate base count
-        get :discussions, namespace_id: project.namespace, project_id: project, id: issue.iid
-
-        RequestStore.clear!
-
-        control_count = ActiveRecord::QueryRecorder.new do
-          get :discussions, namespace_id: project.namespace, project_id: project, id: issue.iid
-        end.count
-
-        RequestStore.clear!
-
-        create_list(:discussion_note_on_issue, 2, :system, noteable: issue, project: issue.project, note: cross_reference)
-
-        expect { get :discussions, namespace_id: project.namespace, project_id: project, id: issue.iid }.not_to exceed_query_limit(control_count)
-      end
-    end
-  end
 end