Bug 796847 - Fix typo in reftest file. rs=npotb DONTBUILD

layout/reftests/bugs/796847-1.svg

@@ -3,7 +3,7 @@
      http://creativecommons.org/publicdomain/zero/1.0/
 -->
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1" class="reftest-wait">
-  <title>Test that the area that's covered by a filtered elemnt is invalidated when content inside it changes</title>
+  <title>Test that the area that's covered by a filtered element is invalidated when content inside it changes</title>
   <filter id="f" x="0" y="0" width="100%" height="100">
     <feGaussianBlur in="SourceGraphic" stdDeviation="0.1"/>
   </filter>