fix mypy

vyper/semantics/types/user.py

@@ -160,7 +160,7 @@ class EventT(_UserType):
 
     _invalid_locations = tuple(iter(DataLocation))  # not instantiable in any location
 
-    def __init__(self, name: str, arguments: dict, indexed: list, is_shadow=False) -> None:
+    def __init__(self, name: str, arguments: dict, indexed: list, is_shadow: bool = False) -> None:
         super().__init__(members=arguments)
         self.name = name
         self.indexed = indexed

vyper/venom/bb_optimizer.py

@@ -74,7 +74,7 @@ def ir_pass_optimize_unused_variables(ctx: IRFunction) -> int:
 
 
 @ir_pass
-def ir_pass_handle_shadow_event_instructions(ctx: IRFunction, shadow_mode=False) -> None:
+def ir_pass_handle_shadow_event_instructions(ctx: IRFunction, shadow_mode: bool = False) -> None:
     """
     Remove unused variables.
     """