Remove SpeechSynthesis runtime flag (status=stable)

BUG=402536

Review URL: https://codereview.chromium.org/482273005

git-svn-id: svn://svn.chromium.org/blink/trunk@180763 bbb929c8-8fbe-4397-9dbb-9b2b20218538
void WebRuntimeFeatures::enableTargetedStyleRecalc(bool enable)
{
    RuntimeEnabledFeatures::setTargetedStyleRecalcEnabled(enable);
}

void WebRuntimeFeatures::enableTargetedStyleRecalc(bool enable)
{
    RuntimeEnabledFeatures::setTargetedStyleRecalcEnabled(enable);
}
