I’ve never tried deleting it, but I have noticed that package myself a few times.
When I copy files into my Steam image, I only copy the most recent changed files. This file is always among them, even though the size has stayed the same for me for quite some time. I therefore often leave it out of updates, and I haven’t noticed any problems.
If you wanted to experiment, you could always move the file, start the game, and see what happens.
P.S.: I just now realized that if that’s a upk file, you should be able to see it in the editor, right?