Remove the unused Renderer client version methods. Previous patches enable us to get rid of this workaround. We should in subsequent patches also try to clean up code that uses the internal Renderer-only version of the context caps. BUG=angle:789 Change-Id: Ic054090303cdc3f7ee8e45e4577c157559955472 Reviewed-on: https://chromium-review.googlesource.com/227714 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Brandon Jones <bajones@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>