Remove query strings

Hi ??

In this report:
https://gtmetrix.com/reports/www.ajibtarin.com/gEiOxYZa

I get some errors in this section:
Remove query strings from static resources

One of them is:
https://cdnajibtarin.ajibtarin.com/wp-content/uploads/ultimatemember/1/profile_photo-190.jpg?1487626821

My developer told me this number generates from here:
/var/www/ajibtarin.com/htdocs/wp-content/plugins/ultimate-member/core/um-short-functions.php

View post on imgur.com

So I want to know is there any way to fix this?

Thanks