pythongh-114331: Skip decimal test_maxcontext_exact_arith on s390x

Author: vstinner

Lib/test/test_decimal.py

@@ -5650,6 +5650,9 @@ def __abs__(self):
     @unittest.skipIf(check_sanitizer(address=True, memory=True),
                      "ASAN/MSAN sanitizer defaults to crashing "
                      "instead of returning NULL for malloc failure.")
+    # gh-114331: The test allocates 784 271 641 GiB and mimalloc does not fail
+    # to allocate it when using mimalloc on s390x.
+    @support.skip_on_s390x
     def test_maxcontext_exact_arith(self):
 
         # Make sure that exact operations do not raise MemoryError due