Correct docstring of Container helper class

The docstring stated that this container implemented legacy
DLPack protocol, while it implements DLPack 1.0

Author: oleksandr-pavlyk

dpctl/tests/test_usm_ndarray_dlpack.py

@@ -750,7 +750,7 @@ def __dlpack_device__(self):
 
 
 class Container:
-    "Helper class implementing legacy `__dlpack__` protocol"
+    "Helper class implementing `__dlpack__` protocol version 1.0"
 
     def __init__(self, array):
         self._array = array