Fix temp dir typing in policy_utils_test

test_convert_to_tflite creates a tempdir using absltest's create_tempdir
function. It then passes this tempdir (which is a _Tempdir type) to a
function expecting a string. This works, but should be using full_path
to keep the internal type checker happy, which this commit does.

Author: boomanaiden154

compiler_opt/es/policy_utils_test.py

@@ -227,7 +227,8 @@ def test_convert_to_tflite(self):
     output_bytes = self.params.tobytes()
 
     scratch_dir = self.create_tempdir()
-    tflite_dir = policy_utils.convert_to_tflite(output_bytes, scratch_dir,
+    tflite_dir = policy_utils.convert_to_tflite(output_bytes,
+                                                scratch_dir.full_path,
                                                 saved_model_path)
 
     self.assertTrue(os.path.exists(os.path.join(tflite_dir, 'model.tflite')))