Remove misleading -> tuple annotation from _normalize

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Roman Korostik <rkorostik@nvidia.com>

Author: racoiaws

nemo/collections/audio/models/audio_to_audio.py

@@ -365,7 +365,7 @@ def _setup_process_dataloader(self, config: Dict) -> 'torch.utils.data.DataLoade
         temporary_dataloader = self._setup_dataloader_from_config(config=DictConfig(dl_config))
         return temporary_dataloader
 
-    def _normalize(self, signal: torch.Tensor) -> tuple:
+    def _normalize(self, signal: torch.Tensor):
         """Normalize signal so its peak amplitude is 1.
 
         Args: