Fix title underline being too short in Running code in the editor

tutorials/plugins/running_code_in_the_editor.rst

@@ -4,7 +4,7 @@ Running code in the editor
 ==========================
 
 What is ``@tool``?
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+------------------
 
 ``@tool`` is a powerful line of code that, when added at the top of your script,
 makes it execute in the editor. You can also decide which parts of the script