FIX: correctly implements average for reports (#13447)

- Also now marks time_to_first_response as an averaged chart
- Averaged charts will now be marked as such in the UI

app/models/concerns/reports/time_to_first_response.rb

@@ -11,6 +11,7 @@ module Reports::TimeToFirstResponse
       report.icon = 'reply'
       report.higher_is_better = false
       report.data = []
+      report.average = true
 
       Topic.time_to_first_response_per_day(report.start_date, report.end_date, category_id: category_id, include_subcategories: include_subcategories).each do |r|
         report.data << { x: r['date'], y: r['hours'].to_f.round(2) }