If you are using a different gun play mod for GTA V and want to remove the flashlight for yourself simply follow these steps.

Open the weaponcomponents.meta in mods\update\update.rpf\common\data\ai\weaponcomponents.meta then find the w_at_ar_flsh under <Name>COMPONENT_AT_AR_FLSH</Name> and change the <MainLightIntensity value and <SecondaryLightIntensity value to 0.000000