Add Deprecation warning for GradNAS

Signed-off-by: Keval Morabia <28916987+kevalmorabia97@users.noreply.github.com>

Author: kevalmorabia97

modelopt/torch/prune/gradnas.py

@@ -181,6 +181,10 @@ def default_search_config(self) -> SearchConfig:
 
     def before_search(self) -> None:
         """Setup search with gradient-based score."""
+        warnings.warn(
+            "GradNAS pruning algorithm is deprecated and will be removed in the future.",
+            DeprecationWarning,
+        )
         # initialize here to keep DMRegistry empty during imports
         GradientBinarySearcher.SETUP_GRADIENT_FUNC = {
             DMRegistry[nn.Linear]: _setup_grad_manager_linear,