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/student-finance-calculator -name '*.html' -print0 | xargs -0 sed -i .bak "s/'/'/g"
    $ git clean -fd test/artefacts/student-finance-calculator/**/*.bak

Author: floehopper

test/artefacts/student-finance-calculator/2015-2016/uk-full-time/6000.0/at-home.html

@@ -32,12 +32,12 @@ <h1>
         <div class="current-question" id="current-question">
             <div class="question">
   <h2>
-    What&#39;s your annual household income?
+    What's your annual household income?
   </h2>
   <div class="question-body">
 
 
-      <p class="hint">This is your parents’ or partner’s gross (pre-tax) income plus your own. It affects how much help you&#39;ll get with living costs.</p>
+      <p class="hint">This is your parents’ or partner’s gross (pre-tax) income plus your own. It affects how much help you'll get with living costs.</p>
 
     <div class="">
 

test/artefacts/student-finance-calculator/2015-2016/uk-full-time/6000.0/at-home/100000.0/children-under-17,dependant-adult,has-disability,low-income.html

@@ -139,13 +139,13 @@ <h3 class="previous-answers-title">
 
 
     <tr class="section">
-    <td class="previous-question-title">What&#39;s your annual household income?</td>
+    <td class="previous-question-title">What's your annual household income?</td>
       <td class="previous-question-body">
       £100,000</td>
 
       <td class="link-right">
           <a href="/student-finance-calculator/y/2015-2016/uk-full-time/6000.0/at-home?previous_response=100000.0">
-            Change<span class="visuallyhidden"> answer to "What&#39;s your annual household income?"</span>
+            Change<span class="visuallyhidden"> answer to "What's your annual household income?"</span>
 </a>      </td>
   </tr>
 

test/artefacts/student-finance-calculator/2015-2016/uk-full-time/6000.0/at-home/100000.html

@@ -145,13 +145,13 @@ <h3 class="previous-answers-title">
 
 
     <tr class="section">
-    <td class="previous-question-title">What&#39;s your annual household income?</td>
+    <td class="previous-question-title">What's your annual household income?</td>
       <td class="previous-question-body">
       £100,000</td>
 
       <td class="link-right">
           <a href="/student-finance-calculator/y/2015-2016/uk-full-time/6000.0/at-home?previous_response=100000.0">
-            Change<span class="visuallyhidden"> answer to "What&#39;s your annual household income?"</span>
+            Change<span class="visuallyhidden"> answer to "What's your annual household income?"</span>
 </a>      </td>
   </tr>