fix(gradual): run post_prepare_cql_cmds

Running of 'post_prepare_cql_cmds' is missed in the perf-regression-predefined-throughput-steps
test. It means that speculative retry was not disabled. It may have an impact on stability
of the test performance

performance_regression_gradual_grow_throughput.py

@@ -121,6 +121,10 @@ def _base_test_workflow(self, workload: Workload, test_name):
             self.wait_no_compactions_running(n=400, sleep_time=120)
             self.run_fstrim_on_all_db_nodes()
 
+        if post_prepare_cql_cmds := self.params.get('post_prepare_cql_cmds'):
+            self.log.debug("Execute post prepare queries: %s", post_prepare_cql_cmds)
+            self._run_cql_commands(post_prepare_cql_cmds)
+
         self.run_gradual_increase_load(workload=workload,
                                        stress_num=stress_num,
                                        num_loaders=num_loaders,