MDL-64107 questions: Increase highlight contrast

When a question has just been edited, it is highlighted. We need to ensure
the colour contrast of text on background is accessible.

mod/quiz/styles.css

@@ -958,7 +958,7 @@ table.quizreviewsummary td.cell {
     background: #e4e4e4;
 }
 
-#categoryquestions > tbody > tr:nth-of-type(even).highlight {
+#categoryquestions > tbody > tr.highlight {
     background-color: #afa;
 }
 

theme/boost/scss/moodle/question.scss

@@ -174,6 +174,10 @@
         }
     }
 
+    .highlight {
+        @extend .text-dark;
+    }
+
     label {
         margin: 0;
         display: block;

theme/boost/style/moodle.css

@@ -8427,10 +8427,10 @@ a.text-danger:hover, a.notconnected:hover, .que a.validationerror:hover, a.text-
 a.text-light:hover, a.text-light:focus {
   color: #dae0e5 !important; }
 
-.text-dark {
+.text-dark, #categoryquestions .highlight {
   color: #373a3c !important; }
 
-a.text-dark:hover, a.text-dark:focus {
+a.text-dark:hover, #categoryquestions a.highlight:hover, a.text-dark:focus, #categoryquestions a.highlight:focus {
   color: #1f2021 !important; }
 
 .text-muted, a.dimmed,