Update minLength.json

Updates the language for the test that verifies that one grapheme is too short when checked against minLength of 2

Author: spacether

tests/draft2020-12/minLength.json

@@ -27,7 +27,7 @@
                 "valid": true
             },
             {
-                "description": "one supplementary Unicode code point is not long enough",
+                "description": "one grapheme is not long enough",
                 "data": "\uD83D\uDCA9",
                 "valid": false
             }