Unmark inspector/elements/edit-dom-actions-shadow.html as flaky

TBR=vsevik
BUG=355459

Review URL: https://codereview.chromium.org/223433003

git-svn-id: svn://svn.chromium.org/blink/trunk@170748 bbb929c8-8fbe-4397-9dbb-9b2b20218538