[cb][tests] 🐛 fix bug in test utils, please merge ASAP (#367)

### [cb][tests] 🐛 fix bug in test utils, please merge ASAP

during some test script refactoring, the parameter `max_model_len` was
overridden to always be 256, even if set differently.

Signed-off-by: Yannick Schnider <[email protected]>

Author: yannicks1

tests/scheduling_utils.py

@@ -60,8 +60,6 @@ def check_scheduler_inference_steps(
     if use_cb:
         monkeypatch.setenv("VLLM_SPYRE_USE_CB", "1")
 
-    max_model_len = 256
-
     # Input parameters sanity check, not actual testing
     # ------
     if not (len(prompts_lengths) == len(seqs_max_tokens)