Bug 1534888 - part2 : move the cue upward 1% of video's height. r=heycam

In `2_cues_overlapping_partially_move_up.vtt`, the second cue was put on the 99% place where the second cue is `1%` higher than the first cue, and then we would move the second cue up by a line box height in order to prevent those two cues overlapping.

Therefore, in the reference files, the second cue should be 1%(of 180px) higher than its original place.

Differential Revision: https://phabricator.services.mozilla.com/D34609

--HG--
extra : moz-landing-system : lando

testing/web-platform/tests/webvtt/rendering/cues-with-video/processing-model/2_cues_overlapping_partially_move_up-ref.html

@@ -22,10 +22,14 @@ body { margin:0 }
     background: rgba(0,0,0,0.8);
     color: green;
 }
+.cueTextGoingUp {
+    position: relative;
+    top: -1.8px; /* 1% height of video's height */
+}
 </style>
 <div class="video">
     <span class="cue">
-        <div><span class="cueText">This is another test subtitle</span></div>
+        <div><span class="cueText cueTextGoingUp">This is another test subtitle</span></div>
         <div><span class="cueText">This is a test subtitle</span></div>
     </span>
 </div>