Unescape HTML-escaped apostrophes in regression test artefacts

Since #2098 & #2112, apostrophes rendered via `SmartAnswer::ErbRenderer` have
not been HTML-escaped. Now that we are rendering question content via this
renderer, we need to update the regression test artefacts for question pages
accordingly.

I ran the following commands to do this:

    $ find test/artefacts/calculate-your-child-maintenance -name '*.html' | xargs sed -i .bak "s/'/'/g"
    $ git clean -fd test/artefacts/calculate-your-child-maintenance/**/*.bak

Author: floehopper

test/artefacts/calculate-your-child-maintenance/pay.html

@@ -37,7 +37,7 @@ <h2>
   <div class="question-body">
 
 
-      <p class="hint">Enter the total number of children - including children that you have family based arrangements for. They will be included in the calculation and you&#39;ll need to supply information about them when arranging Child Maintenance.</p>
+      <p class="hint">Enter the total number of children - including children that you have family based arrangements for. They will be included in the calculation and you'll need to supply information about them when arranging Child Maintenance.</p>
 
     <div class="">