Update on "Introduce data schema to store raw tensors"

Differential Revision: [D65156641](https://our.internmc.facebook.com/intern/diff/D65156641)

[ghstack-poisoned]

Author: lucylq

extension/flat_tensor/common.fbs

@@ -1,7 +1,7 @@
 // Copyright (c) Meta Platforms, Inc. and affiliates.
 
 //
-// See README.md before modifying this file.
+// See executorch/schema/README.md before modifying this file.
 //
 
 namespace executorch_flatbuffer;