Remove (legacy) Models.BoTorch (#2597)

Summary:
Pull Request resolved: #2597

This was deprecated 8 months ago, time to remove it.

Reviewed By: dme65

Differential Revision: D60148734

fbshipit-source-id: ffa88cabd96a87a47f126154f61ab1738efafb65

ax/modelbridge/registry.py

@@ -431,18 +431,6 @@ class Models(ModelRegistryBase):
     ST_MTGP_NEHVI = "ST_MTGP_NEHVI"
     CONTEXT_SACBO = "Contextual_SACBO"
 
-    @classmethod
-    @property
-    def BOTORCH(cls) -> Models:
-        warnings.warn(
-            "`BOTORCH` Model class has been deprecated and renamed to "
-            "`LEGACY_BOTORCH`, and it will be removed in a future release. "
-            "Please use `BOTORCH_MODULAR` instead.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        return cls.LEGACY_BOTORCH
-
     @classmethod
     @property
     def FULLYBAYESIAN(cls) -> Models: