docs(mgb/docs): add alternative interface for deprecated api

GitOrigin-RevId: fdeaa5b64fed0f0bfbe7a0545d32454ab0952bb9

imperative/python/megengine/tensor.py

@@ -197,7 +197,9 @@ class Tensor(_Tensor, ArrayMethodMixin):
         self._name = self._prefix + "." + name if self._prefix else name
         self._set_name(self._name)
 
-    @deprecated(version="1.0", reason="no need to reuse an existing tensor since 1.0")
+    @deprecated(
+        version="1.0", reason="please use ``tensor_name[...] = value``",
+    )
     def set_value(self, value):
         self._reset(value)