libchrome: remove remaining gypi file

TEST=None
BUG=chromium:953642

Change-Id: Ib82b799c244136a6b4a177f55e352208521e20d0
Reviewed-on: https://chromium-review.googlesource.com/1634649
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Keigo Oka <oka@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Reviewed-by: Keigo Oka <oka@chromium.org>