DevTools: NetworkPanel: remove obsolete expectation.

BUG=306228
TBR=loislo@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/646783004

git-svn-id: svn://svn.chromium.org/blink/trunk@183754 bbb929c8-8fbe-4397-9dbb-9b2b20218538