Fix typo in First 3D game - Animating the mobs (#5913)

getting_started/first_3d_game/09.adding_animations.rst

@@ -245,8 +245,8 @@ node structure, you can copy them to different scenes.
 For example, both the *Mob* and the *Player* scenes have a *Pivot* and a
 *Character* node, so we can reuse animations between them.
 
-Open the *Mob* scene, select the animation player node and open the float animation.
-Next, click on *Animation -> Copy*. Then Open ``Player.tscn`` and open its animation
+Open the *Player* scene, select the animation player node and open the float animation.
+Next, click on *Animation -> Copy*. Then Open ``Mob.tscn`` and open its animation
 player. Click *Animation -> Paste*. That's it; all monsters will now play the float
 animation.