git: openjdk/jdk-sandbox: json: TestFormat -> TestGenerate, and some refinement

[duke]

Changeset: 867680f2
Branch: json
Author:    Naoto Sato <naoto.sato at oracle.com>
Date:      2026-01-13 14:35:55 +0000
URL:       https://git.openjdk.org/jdk-sandbox/commit/867680f2de05e67605f2c2aee91d8fd072077237

TestFormat -> TestGenerate, and some refinement

- test/jdk/java/util/json/TestFormat.java
+ test/jdk/java/util/json/TestGenerate.java