Remove lines of CSS which have invalid property values.

BUG=243208
R=dbeam@chromium.org

Review URL: https://chromiumcodereview.appspot.com/15823004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202799 0039d316-1c4b-4281-b951-d872f2087c98

ui/webui/resources/css/bubble.css

@@ -26,7 +26,6 @@
 }
 
 .bubble-close {
-  background-image: no-repeat 50% 50%;
   height: 16px;
   position: absolute;
   right: 6px;

ui/webui/resources/css/expandable_bubble.css

@@ -54,7 +54,6 @@
 }
 
 .expandable-bubble-close {
-  background-image: no-repeat 50% 50%;
   height: 16px;
   position: absolute;
   right: 0;