Adjust test name

By @mbg

Co-authored-by: Michael B. Gale <mbg@github.com>

Author: mario-campos

src/json/index.test.ts

@@ -49,7 +49,7 @@ const optionalSchema = {
   optionalKey: json.optional(json.string),
 };
 
-test("validateSchema - optional properties may be absent or undefined, but reject null", async (t) => {
+test("validateSchema - optional properties are optional", async (t) => {
   // Optional fields may be absent or explicitly undefined
   t.true(json.validateSchema(optionalSchema, {}));
   t.true(json.validateSchema(optionalSchema, { optionalKey: undefined }));