Remove proxy header for ANGLETest.h It is no longer needed as https://codereview.chromium.org/1134953003/ has been landed. BUG=angleproject:892 Change-Id: I3923a7bda2d4a3d70d128f7210fab35837df435d Reviewed-on: https://chromium-review.googlesource.com/272380 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>