revert data dir setter changes because it not needed

Author: Stepan Neretin

testgres/node.py

@@ -441,14 +441,7 @@ def logs_dir(self):
     @property
     def data_dir(self):
         # NOTE: we can't run initdb without user's args
-        if hasattr(self, '_data_dir'):
-            return self._data_dir
-        else:
-            return os.path.join(self.base_dir, DATA_DIR)
-
-    @data_dir.setter
-    def data_dir(self, value):
-        self._data_dir = value
+        return os.path.join(self.base_dir, DATA_DIR)
 
     @property
     def utils_log_file(self):