[Misc] Rename assets for testing (#17575)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/models/multimodal/processing/test_phi4mm.py

@@ -4,7 +4,7 @@ import pytest
 
 from vllm.multimodal import MULTIMODAL_REGISTRY
 
-from ....conftest import _ImageAssets
+from ....conftest import ImageTestAssets
 from ...utils import build_model_context
 
 
@@ -22,7 +22,7 @@ from ...utils import build_model_context
 @pytest.mark.parametrize("num_imgs", [1, 2])
 @pytest.mark.parametrize("kwargs_on_init", [True, False])
 def test_processor_override(
-    image_assets: _ImageAssets,
+    image_assets: ImageTestAssets,
     model_id: str,
     mm_processor_kwargs: dict[str, int],
     expected_toks_per_img: int,