test: drop removed runtime_gather_output arg from process_mtp_loss call

MCore b86e75c18 (Fix vocab-parallel MTP loss for TP>1, NVIDIA/Megatron-LM#7682) removed the runtime_gather_output parameter from process_mtp_loss; the Qwen3-VL text model unit test still passed it.

Signed-off-by: svcnemo-autobot <svcnemo-autobot@nvidia.com>

Author: svcnemo-autobot

tests/unit_tests/models/qwen_vl/modelling_qwen3_vl/test_text_model_forward.py

@@ -263,7 +263,6 @@ def fake_output_layer(hidden, weight=None, runtime_gather_output=None):  # noqa:
         loss_mask=loss_mask,
         output_layer=fake_output_layer,
         output_weight=None,
-        runtime_gather_output=None,
         is_training=False,
         compute_language_model_loss=fake_language_loss,
         config=config,