Move CSSStickyPosition back to status=test
Move CSSStickyPosition back to status=test

We're not actively working on CSSStickyPosition. It's not ready for web
developers to experiment with yet.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/320323002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@175816 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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