DevTools: [CSS] remove unused property status "style" from protocol.json

This patch removes CSSProperty status enum value "style" from
protocol.json due to its redundancy: property.status == "style" iff
property does not have source range.

BUG=341506

Review URL: https://codereview.chromium.org/177863003

git-svn-id: svn://svn.chromium.org/blink/trunk@167707 bbb929c8-8fbe-4397-9dbb-9b2b20218538