Fix: Use literal URL in test_upload_image_asset.py success test

This commit corrects an AttributeError in the `test_main_success` method
of `examples/misc/tests/test_upload_image_asset.py`.

The test was attempting to assert the call to
`get_image_bytes_from_url` using `upload_image_asset.IMAGE_URL`,
but `IMAGE_URL` is not defined as a module-level constant in the
script. The script `upload_image_asset.py` uses a hardcoded URL string
directly within its `main` function.

The assertion has been updated to use the correct literal URL string:
`"https://gaagl.page.link/Eit5"`.

Author: google-labs-jules[bot]

examples/misc/tests/test_upload_image_asset.py

@@ -53,7 +53,7 @@ def test_main_success(self, mock_print):
         upload_image_asset.main(self.mock_client, customer_id)
 
         self.mock_get_image_bytes_from_url.assert_called_once_with(
-            upload_image_asset.IMAGE_URL
+            "https://gaagl.page.link/Eit5"
         )
         self.mock_asset_service.mutate_assets.assert_called_once()