Fix SQL timings for the performance bar

My recent change accidentally changed the reported time from
milliseconds to seconds, resulting in wrong timings being displayed.

lib/gitlab/performance_bar/peek_query_tracker.rb

@@ -36,7 +36,7 @@ module Gitlab
       end
 
       def track_query(raw_query, bindings, start, finish)
-        duration = finish - start
+        duration = (finish - start) * 1000.0
         query_info = { duration: duration.round(3), sql: raw_query }
 
         PEEK_DB_CLIENT.query_details << query_info