wpt: change height of touch target

weblayer shell has a slightly smaller height than chrome. The size is
such that this test ends up failing because the generated touch event
is outside the visible area. This patch shrinks the height slightly
so that it passes on weblayer. I don't believe shrinking the height of
this target impacts the overall test..

BUG=1049426
TEST=test only change

Change-Id: Ie0f2fadc4ec613d92c074b60eb87c97d70f78094
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2112984Reviewed-by: Lan Wei <lanwei@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752214}

third_party/blink/web_tests/external/wpt/pointerevents/pointerevent_touch-action-button-none-test_touch.html

@@ -13,7 +13,7 @@
         <script src="pointerevent_support.js"></script>
         <style>
             #target0 {
-            height: 150px;
+            height: 100px;
             width: 200px;
             overflow-y: auto;
             background: black;