fix: Don't require efficiency_config for torchtune (#2104)

# What does this PR do?

Revert a change that by mistake forced efficiency_config on torchtune
provider
users.

```
    fix: Don't require efficiency_config for torchtune

    It was enforced by mistake when
    0751a96 merged.

    Other asserts made sense in that the code was written, potentially, to
    always expect a non-None value. But not efficiency_config.
```

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

Author: booxter

llama_stack/providers/inline/post_training/torchtune/recipes/lora_finetuning_single_device.py

@@ -39,7 +39,6 @@
 from llama_stack.apis.post_training import (
     Checkpoint,
     DataConfig,
-    EfficiencyConfig,
     LoraFinetuningConfig,
     OptimizerConfig,
     QATFinetuningConfig,
@@ -90,8 +89,6 @@ def __init__(
     ) -> None:
         assert isinstance(training_config.data_config, DataConfig), "DataConfig must be initialized"
 
-        assert isinstance(training_config.efficiency_config, EfficiencyConfig), "EfficiencyConfig must be initialized"
-
         self.job_uuid = job_uuid
         self.training_config = training_config
         if not isinstance(algorithm_config, LoraFinetuningConfig):