in narrow builds, make sure to test codepoints as identifier characters (closes #12732)

This fixes the use of Unicode identifiers outside the BMP in narrow builds.
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 55aaba6..09cf48f 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -404,6 +404,7 @@
         self.assertTrue("bc".isidentifier())
         self.assertTrue("b_".isidentifier())
         self.assertTrue("µ".isidentifier())
+        self.assertTrue("𝔘𝔫𝔦𝔠𝔬𝔡𝔢".isidentifier())
 
         self.assertFalse(" ".isidentifier())
         self.assertFalse("[".isidentifier())