Remove linux-x86 specific test expectation file for imagemap-focus-ring-zero-outline-width.html.

From what I can tell there is no difference between linux and linux-x86 and I also notice that running webkit-patch rebaseline didn't regenerate the linux-x86 file.
Finally there is no .png file for linux-x86 which seems to indicate this is a stale file that is incorrectly picked up when running the test. Hence I am trying to 
remove it to see if the test will start succeeding by picking up the linux version.

BUG=
TBR=eseidel@chromium.org, dglazkov@chromium.org, zhaoze.zhou@partner.samsung.com
NOTRY=true

Review URL: https://codereview.chromium.org/488993002

git-svn-id: svn://svn.chromium.org/blink/trunk@180636 bbb929c8-8fbe-4397-9dbb-9b2b20218538