x11-apps/igt-gpu-tools: Remove from portage-stable

This ebuild differs from upstream so it should be in chromiumos-overlay

BUG=none
TEST=emerge-$BOARD igt-gpu-tools

Cq-Depend: chromium:2238787
Change-Id: If693b41825498683e4e640538faaa7b6198178e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2238806
Tested-by: Drew Davenport <ddavenport@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
3 files changed