release-schema: Clarify pairing of unit scheme and codes

Author: jpmckinney

release-schema.json

@@ -92,7 +92,7 @@
             },
             "scheme": {
               "title": "Scheme",
-              "description": "The list from which units of measure identifiers are taken. It is recommended to use the scheme 'UNCEFACT' for the UN/CEFACT Recommendation 20 list of \"Codes for Units of Measure Used in International Trade\".",
+              "description": "The list from which units of measure identifiers are taken. It is recommended to use the scheme 'UNCEFACT' and codes from the UN/CEFACT Recommendation 20 list of \"Codes for Units of Measure Used in International Trade\".",
               "type": [
                 "string",
                 "null"