CPUParticles2D: Fix gravity to be the same as in Particles2D and Area2D

This was likely a typo, 10 times the standard gravity is 98.0665
(ca. 98), not 98.8.

doc/classes/CPUParticles2D.xml

@@ -118,7 +118,7 @@
 		<member name="fract_delta" type="bool" setter="set_fractional_delta" getter="get_fractional_delta" default="true">
 			If [code]true[/code], results in fractional delta calculation which has a smoother particles display effect.
 		</member>
-		<member name="gravity" type="Vector2" setter="set_gravity" getter="get_gravity" default="Vector2( 0, 98.8 )">
+		<member name="gravity" type="Vector2" setter="set_gravity" getter="get_gravity" default="Vector2( 0, 98 )">
 			Gravity applied to every particle.
 		</member>
 		<member name="hue_variation" type="float" setter="set_param" getter="get_param" default="0.0">

scene/2d/cpu_particles_2d.cpp

@@ -1410,7 +1410,7 @@ CPUParticles2D::CPUParticles2D() {
 	set_emission_sphere_radius(1);
 	set_emission_rect_extents(Vector2(1, 1));
 
-	set_gravity(Vector2(0, 98.8));
+	set_gravity(Vector2(0, 98));
 
 	for (int i = 0; i < PARAM_MAX; i++) {
 		set_param_randomness(Parameter(i), 0);