examples/psycopg2_pool.py: slightly improve output

examples/psycopg2_pool.py

@@ -137,4 +137,4 @@ if __name__ == '__main__':
         gevent.spawn(pool.execute, 'select pg_sleep(1);')
     gevent.run()
     delay = time.time() - start
-    print 'Running "sleep 1" 4 times with 3 threads. Should take about 2 seconds: %.2fs' % delay
+    print 'Running "select pg_sleep(1);" 4 times with 3 connections. Should take about 2 seconds: %.2fs' % delay