Make wait_for_history_jobs look at jobs, not datasets

That fixes test_optional_workflow_output, which started failing after
galaxyproject#17874, which removed the
last static output of `output_filter`, and so there would never be any
active datasets to wait on.

lib/galaxy_test/base/populators.py

@@ -630,7 +630,8 @@ def has_active_jobs():
             raise TimeoutAssertionError(message)
 
         if assert_ok:
-            self.wait_for_history(history_id, assert_ok=True, timeout=timeout)
+            for job in self.history_jobs(history_id=history_id):
+                assert job["state"] in ("ok", "skipped"), f"Job {job} not in expected state"
 
     def wait_for_jobs(
         self,