Set xfail strict.

Author: purple4reina

tests/internal/test_serverless.py

@@ -135,6 +135,8 @@ def find_spec(self, fullname, *args):
             marks=pytest.mark.xfail(
                 reason="throws AttributeError: module 'asyncio.events' has no attribute 'BaseDefaultEventLoopPolicy'",
                 condition=sys.version_info >= (3, 14),
+                # when 3.14 is officially supported, this xfail can be removed.
+                strict=True,
             ),
         ),
         ("ddtrace.propagation.http", "HTTPPropagator"),