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

getting_started/first_3d_game/09.adding_animations.rst

@@ -247,8 +247,8 @@ For example, both the *Mob* and the *Player* scenes have a *Pivot* and a
 
 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 (add an AnimationPlayer child node to Mob it not already done).
-Click **Animation > Paste**. That's it; all monsters will now play the float animation.
+player. Click **Animation > Paste**. That's it; all monsters will now play the float
+animation.
 
 We can change the playback speed based on the creature's ``random_speed``. Open
 the *Mob*'s script and at the end of the ``initialize()`` function, add the