fix(nemesis.py): disrupt_mgmt_restore use right timeout

since we have different snapshots to be used,
with different sizes, the timeout of each one
may differ, and the function was waiting at some
general duration, other than the specified for
each snapshot size.
this change will make it use the specific timeout
for the snapshot selected to the test.

sdcm/nemesis.py

@@ -2815,10 +2815,9 @@ def execute_data_validation_thread(command_template, keyspace_name, number_of_ro
             self.log.info("Restoring the schema of the keyspace '%s'", chosen_snapshot_info["keyspace_name"])
             restore_task = mgr_cluster.create_restore_task(restore_schema=True, location_list=location_list,
                                                            snapshot_tag=chosen_snapshot_tag)
-            step = 10
-            extra_time = 300
-            restore_task.wait_and_get_final_status(step=step,
-                                                   timeout=chosen_snapshot_info['expected_timeout'] / step + extra_time)
+
+            restore_task.wait_and_get_final_status(step=10,
+                                                   timeout=6*60)  # giving 6 minutes to restore the schema
             assert restore_task.status == TaskStatus.DONE, f'Schema restoration of {chosen_snapshot_tag} has failed!'
             self.cluster.restart_scylla()  # After schema restoration, you should restart the nodes