Unmark http/tests/inspector/elements/styles/selector-line-sourcemap-header-deprecated.html as flaky

TBR=vsevik
BUG=353179

Review URL: https://codereview.chromium.org/223493002

git-svn-id: svn://svn.chromium.org/blink/trunk@170751 bbb929c8-8fbe-4397-9dbb-9b2b20218538