test_partitioner_with_spec: accept Python 3.12 setter error message

Summary:
Python 3.12 changed the AttributeError message emitted when assigning to a property without a setter, from "can't set attribute 'spec'" to "property 'spec' of 'CustomPartitioner' object has no setter". The `assertRaisesRegex` in `test_partitioner_with_spec` only matched the pre-3.12 form, so the test failed on the Python 3.12 runtime.

Updated the regex to match either form. 

Authored with Claude.

Differential Revision: D104316540

Author: rascani

exir/backend/test/test_partitioner.py

@@ -106,7 +106,7 @@ def partition(
 
         with self.assertRaisesRegex(
             AttributeError,
-            "can't set attribute 'spec'",
+            r"(can't set attribute 'spec'|property 'spec' of .* object has no setter)",
         ):
             my_partitioner.spec = {"new_key": "new_value"}