Remove Overridden Question Attributes in Docs (#2513)

The docs currently has a question where there are slots overriding
the header attributes. However, when #2511 is merged, logger
warnings about this overriding will be triggered, leading to the
check-docs GitHub action failing.

Let's remove the header attributes so that they will not trigger
the logger warning. Let's also update the sample code to reflect
this change.

docs/userGuide/syntax/questions.md

@@ -59,7 +59,7 @@ If you require more expressive formatting for your header or hint markup, you ca
 <variable name="highlightStyle">html</variable>
 <variable name="heading">Headers and Hints using slots</variable>
 <variable name="code">
-<question type="checkbox" header="Which of the following is true?" hint="Think out of the box! :fas-box:">
+<question type="checkbox">
   <!-- Header slot -->
   <div slot="header">
 
@@ -86,7 +86,7 @@ If you require more expressive formatting for your header or hint markup, you ca
 </question>
 </variable>
 <variable name="output">
-<question type="checkbox" header="Which of the following is true?" hint="Think out of the box! :fas-box:">
+<question type="checkbox">
   <!-- Header slot -->
   <div slot="header">