[api] Refactor StatisticsCalculations class

* Sort results right away instead of temporarely storing it
* Shorten how we apply the limit

src/api/lib/statistics_calculations.rb

@@ -12,9 +12,8 @@ def self.get_latest_updated(limit = 10, timelimit = Time.at(0), prj_filter = ".*
                pluck(:name, :updated_at).
                map { |name, at| [at, name, :project] }
 
-    list = packages + projects
-    list.sort! { |a, b| b[0] <=> a[0] }
-    return list if limit.nil?
-    list.first(limit)
+    list = (packages + projects).sort { |a, b| b[0] <=> a[0] }
+
+    limit ? list.first(limit) : list
   end
 end