Skip a test with unicode supplementary characters

Author: otethal

graalpython/lib-python/3/test/test_json/test_scanstring.py

@@ -1,8 +1,10 @@
 import sys
 from test.test_json import PyTest, CTest
+from test import support
 
 
 class TestScanstring:
+    @support.impl_detail(msg="not yet supported: GR-26305 unicode supplementary characters", graalvm=False)
     def test_scanstring(self):
         scanstring = self.json.decoder.scanstring
         self.assertEqual(