[CI][TPU] Skip Multimodal test (#17488)

Signed-off-by: Siyuan Liu <lsiyuan@google.com>

tests/v1/tpu/test_multimodal.py

@@ -32,6 +32,8 @@ def base64_encoded_image() -> dict[str, str]:
 async def test_basic_vision(model_name: str, base64_encoded_image: dict[str,
                                                                         str]):
 
+    pytest.skip("Skip this test until it's fixed.")
+
     def whats_in_this_image_msg(b64):
         return [{
             "role":