Clarify skip in test_strtod

Lib/test/test_strtod.py

@@ -146,8 +146,7 @@ class StrtodTests(unittest.TestCase):
                     digits *= 5
                     exponent -= 1
 
-    # TODO: RUSTPYTHON fails on debug mode, flaky in release mode
-    @unittest.skip
+    @unittest.skip("TODO: RUSTPYTHON, fails on debug mode, flaky in release mode")
     def test_halfway_cases(self):
         # test halfway cases for the round-half-to-even rule
         for i in range(100 * TEST_SIZE):