ci: Bump the llvmpipe test timeout to 240 seconds

lp_test_blend occasionally exceeds this on s390x, but we don't really
want to lose what little (hah) big-endian coverage we have.

Related: #3437
Acked-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <!9921>
56 jobs for !9921 with s390x-test-timeout in 13 minutes and 9 seconds (queued for 4 seconds)
latest merge request