How to Install:
Download the program OpenIV, open it and locate your GTA V folder > update > update.rpf > x64 > data > cdimages > scaleform_generic.rpf > click edit on the top> put the hud_reticle.gfx here

if you use the mods folder:
mods > update > update.rpf > x64 > data > cdimages > scaleform_generic.rpf > click edit on the top> put the hud_reticle.gfx here

So, I've seen someone make No reticle and no hitmark mod and it involves disabling it through the frontend.xml file... But if they did that, it will disable the entire crosshair(makes it really hard to play in 3rd person view) including the sniper rifle sight..

What i did is I make the Hitmarker texture inside the hud_reticle.gfx become transparent, technically it will still appear but you won't see any of it (the hitmarker is completely Transparent). On the screenshot, you could see the hitmarker texture (shape 6 and shape 7) is completely blank.

Remember to backup your update.rpf file
I'm one of those person that hate hitmarker but love crosshair :)
enjoy