Cleanup in stub-cache.cc; remove unused ArrayLength store ICs.

BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/430783002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22805 ce2b1a6d-e550-0410-aec6-3dcde31c8c00