try to fix unforeseen behaviour of ci run

mlair/run_modules/pre_processing.py

@@ -216,7 +216,7 @@ class PreProcessing(RunEnvironment):
         valid_stations = []
         kwargs = self.data_store.create_args_dict(data_handler.requirements(), scope=set_name)
 
-        if os.cpu_count() > 1:  # parallel solution
+        if multiprocessing.cpu_count() > 1:  # parallel solution
             logging.info("use parallel validate station approach")
             pool = multiprocessing.Pool()
             output = [