D3D11: Remove unused mRenderer from VertexArray11. This was uncovered by the Clang-win bot, which uses a different set of warnings from MSVS. BUG=angleproject:1327 Change-Id: Id298fee2df92752b77bf6e2b93307fa5311cf1fc Reviewed-on: https://chromium-review.googlesource.com/332035 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>