[mediaqueries-5] Bikeshed markup fix

Author: frivoal

mediaqueries-5/Overview.bs

@@ -186,7 +186,7 @@ Detecting the display technology: the 'environment-blending' feature</h3>
             For example: an LCD display embedded in a bathroom mirror.
     </dl>
 
-    Issue: Is there a need for the 'subtractive' value?
+    Issue: Is there a need for the ''subtractive'' value?
 
     <div class="example">
         <pre>