Refactor the rain lighting decision operator

Use a simple ternary operator to fill the HSV variable with zeros
or randomised hue and saturation values. This change reduces output
firmware size.

quantum/rgb_matrix/animations/pixel_rain_anim.h

@@ -16,13 +16,9 @@ static bool PIXEL_RAIN(effect_params_t* params) {
         if (!HAS_ANY_FLAGS(g_led_config.flags[led_index], params->flags)) {
             return;
         }
-        if (random8() & 2) {
-            rgb_matrix_set_color(led_index, 0, 0, 0);
-        } else {
-            HSV hsv = {random8(), random8_min_max(127, 255), rgb_matrix_config.hsv.v};
-            RGB rgb = rgb_matrix_hsv_to_rgb(hsv);
-            rgb_matrix_set_color(led_index, rgb.r, rgb.g, rgb.b);
-        }
+        HSV hsv = (random8() & 2) ? (HSV){0, 0, 0} : (HSV){random8(), random8_min_max(127, 255), rgb_matrix_config.hsv.v};
+        RGB rgb = rgb_matrix_hsv_to_rgb(hsv);
+        rgb_matrix_set_color(led_index, rgb.r, rgb.g, rgb.b);
         wait_timer = g_rgb_timer + interval();
     }