fix gpu_particles_3d randomizing seed when set_one_shot is called

Author: TCROC

scene/2d/gpu_particles_2d.cpp

@@ -912,6 +912,8 @@ GPUParticles2D::GPUParticles2D() {
 	one_shot = false; // Needed so that set_emitting doesn't access uninitialized values
 	set_emitting(true);
 	set_one_shot(false);
+	set_use_fixed_seed(false);
+	set_seed(0);
 	set_amount(8);
 	set_amount_ratio(1.0);
 	set_lifetime(1);

scene/3d/gpu_particles_3d.cpp

@@ -92,10 +92,6 @@ void GPUParticles3D::set_one_shot(bool p_one_shot) {
 
 	if (is_emitting()) {
 		if (!one_shot) {
-			if (!use_fixed_seed) {
-				set_seed(Math::rand());
-			}
-
 			RenderingServer::get_singleton()->particles_restart(particles);
 		}
 	}