Use Gitlab::Vulnerability::Summary to get summary

ee/app/controllers/concerns/project_vulnerability_findings_actions.rb

@@ -23,11 +23,11 @@ module ProjectVulnerabilityFindingsActions
   end
 
   def summary
-    vulnerabilities_summary = vulnerability_findings.counted_by_severity
+    summary = Gitlab::Vulnerabilities::Summary.new(group, filter_params).vulnerabilities_counter
 
     respond_to do |format|
       format.json do
-        render json: VulnerabilitySummarySerializer.new.represent(vulnerabilities_summary)
+        render json: summary
       end
     end
   end