[Cleanup] Removing remaining traces of lazy-block implementation from CSSValueKeywords.in

It was added as a part of this patch
https://codereview.chromium.org/13937017

The patch was reverted here
https://chromiumcodereview.appspot.com/23072015

Review URL: https://codereview.chromium.org/322103003

git-svn-id: svn://svn.chromium.org/blink/trunk@175883 bbb929c8-8fbe-4397-9dbb-9b2b20218538