Framebuffer: Remove ext check for depth/stencil textures. The absence of the extension should not prevent depth/stencil textures in FBOs in ES3, since they are core. In fact it shouldn't be possible to make depth/stencil attachments at all without support, so the check shouldn't be necessary. BUG=angleproject:1828 Change-Id: Ibec1e95c78b79cec9654f06ba11beec447017f1c Reviewed-on: https://chromium-review.googlesource.com/438604 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>