fix(ci): cap VLABench smoke eval at 50 steps per task

VLABench's default episode_length is 500 steps; with 10 tasks at ~1 it/s
the smoke eval took ~80 minutes of rollouts on top of the image build.
The eval is a pipeline smoke test (running_success_rate stays at 0% on
this short rollout anyway), so we don't need full episodes — cap each
task at 50 steps to bring total rollout time down ~10x.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/benchmark_tests.yml

@@ -900,6 +900,7 @@ jobs:
                 --policy.path=lerobot/smolvla_vlabench \
                 --env.type=vlabench \
                 --env.task=select_fruit,select_toy,select_book,select_painting,select_drink,select_ingredient,select_billiards,select_poker,add_condiment,insert_flower \
+                --env.episode_length=50 \
                 --eval.batch_size=1 \
                 --eval.n_episodes=1 \
                 --eval.use_async_envs=false \