[video] Remove video_007 test

According to W3C specification the HTMLMediaElement.startTime has
been removed from the HTMLMediaElement. Thus the test which tests
startTime is useless.

For details see:
http://www.w3.org/TR/html5/embedded-content-0.html#media-elements

Change-Id: I123134e5eefb7cc75585520de2788ea8e265fab4
Merge pull request #557 from tiwanek/XWALK-2206

[video] Remove video_007 test