Apply gravity to Red Robot while idle

[aidan-j-rhoden]

When the player first enters a red robot's detection collider, it drops to the floor and then approaches the player. This is because they are placed slightly above the ground in level.tscn, as it is somewhat hard to get just perfect.

I added a line in red_robot.gd to apply gravity while it is idling, so it doesn't just hover there.

[Calinou]

Tested locally, it works. Thanks!