Gardening: Mark http/tests/inspector/styles/selector-line-deprecated.html as flaky

TBR=pfeldman@chromium.org
BUG=331572

Review URL: https://codereview.chromium.org/124243002

git-svn-id: svn://svn.chromium.org/blink/trunk@164462 bbb929c8-8fbe-4397-9dbb-9b2b20218538