Move test_shark_model_suite job to postsubmit only. (#10576)
Move test_shark_model_suite job to postsubmit only. (#10576)

The tests added in https://github.com/iree-org/iree/pull/9748 started
failing (see https://github.com/nod-ai/SHARK/issues/373), so this moves
the tests to postsubmit so they don't block PRs. We could also disable
them pending a fix.

See also: https://github.com/iree-org/iree/issues/9537
google/iree,google/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,google/iree,iree-org/iree