python-dateutil: add overload to rrulestr (#14815)

stubs/python-dateutil/@tests/test_cases/check_rrule.py

@@ -0,0 +1,13 @@
+from typing import Union
+from typing_extensions import assert_type
+
+from dateutil.rrule import rrule, rruleset, rrulestr
+
+rs1 = rrulestr("", forceset=True)
+assert_type(rs1, rruleset)
+
+rs2 = rrulestr("", compatible=True)
+assert_type(rs2, rruleset)
+
+rs3 = rrulestr("")
+assert_type(rs3, Union[rrule, rruleset])