Adjust test name again

By @mbg

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

Author: mario-campos

src/json/index.test.ts

@@ -28,7 +28,7 @@ test("validateSchema - required properties are required", async (t) => {
   t.true(json.validateSchema(testSchema, { requiredKey: "foo" }));
 });
 
-test("validateSchema - optional properties are optional", async (t) => {
+test("validateSchema - optionalOrNullSchema properties are optional or null", async (t) => {
   // Optional fields may be absent
   t.true(json.validateSchema(optionalOrNullSchema, {}));
   t.true(json.validateSchema(optionalOrNullSchema, { optionalKey: undefined }));