UI/Code a lifebar: Fix image caption

getting_started/step_by_step/ui_code_a_life_bar.rst

@@ -100,7 +100,7 @@ scene:
 
 .. figure:: img/lifebar_tutorial_Player_with_editable_children_on.png
 
-       lifebar_tutorial_Player_with_editable_children_on.png
+       The scene tree, with the Player scene set to display its children
 
 Set up the Lifebar with the Player's max\_health
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