chore: address review comments

litestar/_signature/types.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Any, Callable, ClassVar
+from typing import Any
 
 from msgspec import ValidationError
 
@@ -9,7 +9,3 @@ class ExtendedMsgSpecValidationError(ValidationError):
     def __init__(self, errors: list[dict[str, Any]]) -> None:
         self.errors = errors
         super().__init__(errors)
-
-
-class SerializationWrapper:
-    _decoder: ClassVar[Callable[[type, Any], Any]]