Keep *External/* disabled, because capturing of external
textures is not supported.

Bug: angleproject:6034
Bug: angleproject:6035
Bug: angleproject:6036
Bug: angleproject:6041
Change-Id: Id5eb9dc7c651240d0ba094be964d8bd141d08ff9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2944957
Commit-Queue: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>