Update "Dodge the Creeps" demo

[dalexeev]

• Fix AnimatedSprite2D (playing → play(), frames → sprite_frames).
• emit_signal("signal_name") → signal_name.emit().
• Use Array.pick_random() instead of randi() % array.size().
• Use Vector2.clamp() instead of clamp() on components.
• Use StringName literals for consistency.
• Switch renderer to Vulkan Mobile to match description in README (this is a bug due to project setting rename).

[akien-mga]

Thanks!