ci: Disable scons-win64 job

It's failed for almost a month, so right now it's mostly noise and a
waste of CI resources.

It can easily be re-enabled by an MR which makes it pass again.

Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <!8976>
92 jobs for !8976 with ci-scons-win64-disable in 13 minutes and 43 seconds (queued for 6 seconds)
merge request