Slow down passenger spawning rate due to extra time spent on metro car changing speed and moving passengers

Author: yanfengliu

src/config.py

@@ -42,7 +42,7 @@
 passenger_size = 5
 passenger_color = (128, 128, 128)
 passenger_spawning_start_step = 1
-passenger_spawning_interval_step = 10 * framerate
+passenger_spawning_interval_step = 15 * framerate
 passenger_display_buffer = 3 * passenger_size
 passenger_max_wait_time_ms = 60_000
 passenger_blink_warning_time_ms = 10_000