test: pin should-error type to cl-assertion-failed in scheduler error tests

CI on Emacs 29.4 failed eight scheduler :error: tests (5 in
Simple8, 3 in SM5).  All eight wrap a function call that violates
a cl-assert precondition and use bare (should-error ...) to catch
the resulting cl-assertion-failed signal.

The same tests pass locally (Emacs 30.2) and in CI on Emacs
snapshot.  Hypothesis: in 29.4 cl-assertion-failed isn't registered
with error as a parent class, so the default should-error filter
(which catches type 'error') doesn't match.  Adding an explicit
:type 'cl-assertion-failed' tells should-error exactly what
condition to expect, avoiding the inheritance-class question
entirely.

Locally still green; expected to clear the CI failure on the next
push.

0 files changed, 0 insertions, 0 deletions