refactor: remove redundant cast

tests/conftest.py

@@ -10,4 +10,4 @@ def google_calendar_file() -> typing.Iterator[io.BufferedReader]:
     with pathlib.Path(__file__).parent.joinpath(
         "resources", "google-calendar.ics"
     ).open("rb") as file:
-        yield typing.cast(io.BufferedReader, file)
+        yield file