Draft: CI: Temporarily disable Panfrost T7x0

Please do not merge this yet; the downtime is scheduled for Thurs 3rd Sep, 8-11am UTC

We're having rolling lab downtime, and these are the only two devices which aren't yet sharded across redundant dispatchers. Given that we don't know exactly how long they might be down for, disable them until all the work is done.

Signed-off-by: Daniel Stone daniels@collabora.com