Update on "[executorch][schema] Add 'EXTERNAL' to DataLocation in schema"

To indicate if a tensor is external to the PTE file or not.

Currently, we can also use the existence of 'fqn' to determine if a tensor is external or not.
I think it's better to have a specific location field as fqn may be required for cases besides external tensor storage.

Differential Revision: [D66523171](https://our.internmc.facebook.com/intern/diff/D66523171/)

[ghstack-poisoned]

Author: lucylq

exir/schema.py

@@ -72,7 +72,6 @@ class Tensor:
 
     # check program.fbs for explanations.
     shape_dynamism: TensorShapeDynamism
-    location: DataLocation
     extra_tensor_info: Optional[ExtraTensorInfo] = None