fix(python-filtering): update filtering example with optional return type in Python (#11790)

Author: Lujeni

docs/platforms/python/configuration/filtering/index.mdx

@@ -30,7 +30,7 @@ Suppose that you wish prevent all errors of type `ZeroDivisionError` from being
 import sentry_sdk
 from sentry_sdk.types import Event, Hint
 
-def my_before_send(event: Event, hint: Hint) -> Event:
+def my_before_send(event: Event, hint: Hint) -> Event | None:
     # Filter out all ZeroDivisionError events.
     # Note that the exception type is available in the hint,
     # but we should handle the case where the exception info