Add a @note to rg_fire_bullets3 at include

[RauliTop]

This 3 natives: https://github.com/Vaqtincha/reapi/blob/84b61c12cc799113c3c5a4e4c643eaa5ce0e7633/reapi/extra/amxmodx/scripting/include/reapi_gamedll.inc#L327#L380

To avoid confusion, I think it will be a good idea to add a @ note that the natives can't create a decal effect.
Also at rg_fire_bullets3 add too: can't create shot sound, shot animation, clip decreased, etc.
Tested and more info here: https://dev-cs.ru/threads/17498/#post-112767