Mark test_correctly_rounded_true_division as cpython specific

Author: otethal

graalpython/com.oracle.graal.python.test/src/tests/unittest_tags/test_long.txt

@@ -3,6 +3,7 @@
 *graalpython.lib-python.3.test.test_long.LongTest.test_bit_length
 *graalpython.lib-python.3.test.test_long.LongTest.test_bitop_identities
 *graalpython.lib-python.3.test.test_long.LongTest.test_conversion
+*graalpython.lib-python.3.test.test_long.LongTest.test_correctly_rounded_true_division
 *graalpython.lib-python.3.test.test_long.LongTest.test_division
 *graalpython.lib-python.3.test.test_long.LongTest.test_float_conversion
 *graalpython.lib-python.3.test.test_long.LongTest.test_float_overflow

graalpython/lib-python/3/test/test_long.py

@@ -821,6 +821,7 @@ def check_truediv(self, a, b, skip_small=True):
         self.assertEqual(expected, got, "Incorrectly rounded division {}/{}: "
                          "expected {}, got {}".format(a, b, expected, got))
 
+    @support.impl_detail("cpython specific", graalvm=False)
     @support.requires_IEEE_754
     def test_correctly_rounded_true_division(self):
         # more stringent tests than those above, checking that the